Larynx descent in male and female deer

Larynx descent in male and female deer

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Male red deer (Cervus elaphus) and Male Fallow deer (Dama dama) have a descended larynx, presumably for size exaggeration - to attract mates and intimidate other animals.

  1. Does this descent occur after sexual maturation?

  2. Do females of these species also have descended larynx?

  3. In males, does this occur twice - just as it does with human males?

  4. Do deer use size exaggeration to intimidate other animals, other male deer only or both?

  5. Lastly, are there other typical behaviors associated with size exaggeration (i.e. standing on back legs)?

Thank you in advance. I attempted to search for these online but so far have not found any answers. Of course, any cite-able literature containing the answers would be ideal.

Père David's Deer

IV.A. Pedigree Management in Very Small Populations

Olney et al. (1994) describe examples of multi-institutional breeding plans with genetic components for numerous species, including Przewalski's horse, Père David's deer ( Elaphurus davidianus), Hawaiian goose (Branta sandvicensis), California condor (Gymnogyps californianus), and Tahitian Partula tree snails, all of which were extirpated in the wild. Cases of more intensive genetic management, including the establishment of relationships, founder representation, and breeding to maximize Ne, include captive populations of lion-tailed macaque (Macaca silenus) (San Diego Zoo), Speke's gazelle (Gazella spekei) (St. Louis Zoo), Waldrapp ibis (Geronticus eremita) (Zurich Zoo), Guam rail (Rallus owstoni), Micronesian kingfisher (Halcyon cinnamomina), and Mauritius pink pigeon (Nesoenas mayeri). Genetic sex determination of juvenile California condors enabled recovery program managers to pair birds efficiently.

Geneticists have identified low genetic variability as a concern in wild and captive populations of many species, including cheetah, Californian Channel Island fox (Urocyon littoralis), Newfoundland black bear (Ursus americanus), Gir Forest Asian lions (Panthera leo), southern koalas (Phascolarctus cinereus), European bison (Bison bonasus), Arabian oryx (Oryx leucoryx), Père David's deer, and Torrey pine (Pinus torreyana). A loss of self-incompatibility alleles may pose a threat to reproduction in plants with genetically determined self-incompatibility systems such as the rare lakeside daisy (Hymenoxys acaulis) in Illinois.

Geneticists identified inbreeding as a probable cause of reproductive failures in populations of Ngorongoro lions (Panthera leo), Florida panther (Puma concolor coryi), Barrow Island black-footed rock wallaby (Petrogale lateralis), bighorn sheep (Ovis canadensis), Puerto Rican parrot (Amazon vittata), and the Isle Royale gray wolf (Canis lupus).


In many polygynous ruminants, harem-holding males produce rutting calls as a prominent part of courtship behaviour [1,2,3,4,5,6,7]. Male rutting display attracts potential mating partners [8], affects female ovulation [9, 10] and deters rival males [11,12,13]. As in many ruminants, vocalization is a remarkable part of the rutting display in territorial rutting male impala Aepyceros melampus [14,15,16,17,18]. The rutting vocal display of male impala comprises bouts of roars and snorts [18].

Acoustic traits of rutting calls in ruminants indicate male quality [1, 19, 20], such as a caller’s body size [4, 5, 8, 13, 20,21,22], age [4, 5, 23], physical condition [24,25,26], emotional arousal [27, 28] and dominance [20, 22, 29, 30]. Receptive females are responsive to the traits correlating with large male body size, e.g. the lowered vocal tract resonance frequencies (i.e. formants) of rutting calls as a consequence of longer vocal tracts in larger males [8, 21, 31, 32]. However, see [33] for alternative results.

Sexual selection for rutting calls with low formants may result in a morphological specialization of the male vocal apparatus, including a retractable larynx or an extensible nose. The retractable larynx elongates the vocal tract caudally towards the sternum [34,35,36], whereas an extensible nose elongates the vocal tract rostrally [7, 37]. Lowered formants as acoustic correlates of an elongated vocal tract during the emission of male rutting calls have been considered as an adaptation for exaggerating apparent body size [34]. Lowered formants due to retraction of the larynx were found in rutting male goitred gazelle Gazella subgutturosa [36, 38], red deer Cervus elaphus [4, 5, 34, 39], fallow deer Dama dama [35] and impala [18].

Another acoustic trait of male quality, a low fundamental frequency (f0 below 50 Hz), i.e. the rate of vocal fold vibration, may be effective for deterring male rivals in polygynous ruminants, such as in fallow deer [13]. In contrast, females of red and sika deer Cervus nippon appear to react indifferently towards a low fundamental frequency [31, 40]. However, a correlation between a low f0 and male reproductive success has not yet been documented for polygynous ruminants.

In some ruminants, the male larynx is noticeably enlarged [36, 38, 41]. This enlargement, as in Mongolian gazelle Procapra gutturosa [42,43,44], fallow deer [22, 45] and goitred gazelle [36, 41], may result from sexual selection for a visual signal of high testosterone levels in harem-holding males [36, 41]. In male goitred gazelle, the enlargement of the larynx entails a respective enlargement of the vocal folds, producing rutting roars with an f0 of 23 Hz [38, 41]. The larynx of male impala is not noticeably enlarged, but the vocal folds within the larynx are strongly enlarged and modified and are capable of producing rutting roars with an f0 of 50 Hz [18].

A particularly remarkable trait of male impala rutting vocal display is pant-roaring with a rapid alternation of inhalatory and exhalatory vocalization phases [14,15,16, 18]. Pant-calls are also reported for two species of marsupials [46,47,48], two species of rhinos [49,50,51] and three species of primates [52,53,54,55]. Potentially, and in addition to low fundamental and formant frequencies, the rapid alternation of inhalatory and exhalatory phases in male impala rutting calls may function as a further acoustic trait of male quality in harem-holding mammals. However, this function has not been investigated yet. Detailed analysis of the pant-roars in male impala is necessary to provide a basis for future playback studies investigating the potential role of pant-roars as indicators of male quality.

Male impala bouts of rutting calls include three types of roars, differing by the underlying breathing mode [18]. The first type is the continuous roar, with a single exhalatory-inhalatory cycle, the second type is the interrupted roar with few interspersed inhalations and the third type is the pant-roar including a part with a rapid alternation of exhalatory and inhalatory phases [18]. Therefore, male impala may serve as a convenient model for investigating the effects of a panting mode of vocal production on the acoustic traits. Although the different types of roars were already identified in a preceding study [18], the acoustic features of these calls have not yet been investigated in detail and the boundaries between these call types have not yet been established.

In addition to the roars, male impala produce snorts within bouts of rutting calls [18]. Similarly sounding snorts can also be produced when they spot a potential danger [56]. This context-sharing of snort vocalization is reminiscent of the situation in male topi antelope Damaliscus lunatus, which produce snorts in both rutting and alarm contexts [57]. In topi, the rutting and alarm snorts are acoustically identical and are equally effective for attracting the attention of receptive females [57]. For male impala, similarity or difference between the rutting and alarm snorts has not yet been demonstrated. The use of snorts in different contexts is interesting though as a potential further example of mate guarding via a sensory exploitation mechanism.

The aim of this study was to investigate the complex rutting vocal display and its overlap with alarm calls in free-ranging male impala Aepyceros melampus in Namibia. We analyse in detail the complex structure of male impala bouts of rutting calls. We compare the acoustics of different call types within bouts and estimate a potential influence of additional short inhalations and the panting mode of vocal production on the acoustics of the rutting roars. In addition, we compare the acoustic structure of snorts between rutting and alarm contexts.

Female red deer prefer the roars of larger males

Surprisingly little is known about the role of acoustic cues in mammal female mate choice. Here, we examine the response of female red deer (Cervus elaphus) to male roars in which an acoustic cue to body size, the formants, has been re-scaled to simulate different size callers. Our results show that oestrous red deer hinds prefer roars simulating larger callers and constitute the first evidence that female mammals use an acoustic cue to body size in a mate choice context. We go on to suggest that sexual selection through female mating preferences may have provided an additional selection pressure along with male–male competition for broadcasting size-related information in red deer and other mammals.


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In agreement with Prediction 1 (“males get ready prior to females’ arrival”), competitively stronger males—older and heavier bucks with larger antlers—moved to the lek prior to younger bucks and subadult males, well before the beginning of the rut and the arrival of females. In disagreement with Prediction 2 (“first come first served”), arriving earlier at the lek did not guarantee any higher chance to defend the territory for a longer period nor to achieve any higher mating success. Early arrival at the lek seemed to be a necessary—older and heavier bucks moved to the mating site roughly 1 month prior to the peak of the rut—but not sufficient condition to be successful, in agreement with Prediction 3 (“no guarantee of success for early arrivals”). In fact, the ability to defend a lek territory for longer (but not the ability to achieve a higher mating success) was positively related to age, body mass, and antler length, but not arrival time. Older and successful males left the lek later than younger and unsuccessful bucks and subadult males, clearly in disagreement with Prediction 4 (“seeking compensation for low mating success”). Adult males seeking for a chance to defend a territory and mate have to go to the lek well before the beginning of the rut and stay there at least until the end of it, though this does not guarantee them any higher mating success.

Few studies have investigated how behaviors prior to the breeding season may influence mate choice and mating success. Why do males move to the lek more than 1 month prior to the peak of the rut? We cannot fully answer this question, as our data do not support a direct link between arrival time and mating success. However, here we suggest a number of not mutually exclusive explanations:

a) In several vertebrates that hibernate but do not form male dominance hierarchies nor defend territories, for example, garter snake Thamnophis sirtalis parietalis ( Gregory 1974) and echidnas Zaglossus bartoni ( Beard et al. 1992), males often emerge earlier than females likely because they may be at a disadvantage for not being present when the first females emerge. This may apply to lekking males as well. In addition, estrus in primiparous female fallow deer begins earlier during the mating season ( Briefer et al. 2013) and males may increase the likelihood to mate with them if they move to the lek earlier.

b) In many bird species, prior to the mating season, males exhibit behaviors resembling the ones typically performed during the breeding season. For instance, in the lekking black grouse Tetrao tetrix, both males and females regularly visit leks in autumn, even though the mating season occurs in spring. Male black grouses establishing their territories in autumn enjoy higher copulation success than those arriving during the actual mating season, that is, in spring ( Rintamäki et al. 1999). This behavior may contribute to establishing male hierarchy, as well as providing females with the opportunity to assess males prior to the breeding season ( Rintamäki et al. 1999). The former explanation is more likely to apply to our case study on fallow deer because females do not visit leks prior to the beginning of the rut ( Apollonio et al. 2014). However, the importance of lek attendance prior to the mating season may play a role in other lekking species in which females do visit the lek prior to their mating ( Fiske and Kalas 1995 Rintamaki et al. 1995 Fiske et al. 1998).

c) In ungulates, it is thought that male–male combats prior to and during the breeding season ( Mysterud et al. 2005 Mainguy and Cote 2008 Taillon and Cote 2008) as well as visual displays and noncontact interactions are decisive in hierarchy settlement ( Jennings et al. 2002). In this context, vocal communication can contribute to decrease the need to fight because the acoustic structure of male vocalizations was showed to be individually distinctive and contain information on male body mass and/or dominance status ( Reby et al. 1998 McElligott et al. 2006 Vannoni and McElligott 2007, 2008 Wyman et al. 2008 Vannoni and McElligott 2009). Indeed, in polygynous mating systems with high levels of male competition and low levels of paternal care, high-ranking dominant males obtain more copulations than low-ranking males ( Appleby 1982 Katano 1990 Cowlishaw and Dunbar 1991 Choe 1994 Hoelzel et al. 1999). Thus, it appears crucial to occupy a high-ranking position since the beginning. Social dominance achieved before the rut may reduce the costs of conflict by ending an interaction prior to physical engagement ( Gosling et al. 1996), thus avoiding the loss of females within the territories, injury, or death ( Clutton-Brock et al. 1988 Apollonio et al. 1989). As regards nonlekking fallow deer, McElligott et al. (1998) showed that males established dominance rank mainly by noncontact agonistic interactions during the pre-rut period and carried it over during the rut, when it was correlated with mating success. Vannoni and McElligott (2009) also indicated that higher-ranked fallow bucks started groaning several weeks before the first mating ( McElligott and Hayden 1999 McElligott et al. 1999). Dominance hierarchy in fallow deer is thought to be partly established prior to moving to the lek ( Chapman D and Chapman N 1997 Ciuti et al. 2011) and thus the month prior to the rut may have the function to reinforce such hierarchy. In conclusion, it is possible that fallow deer bucks build a part of their oncoming success in the lek during the pre-rut period, but more data (e.g., on male–male interactions, see Figure 5b) should be collected.

d) Marking activities around the fallow deer lek, which are thought to be important for male status signaling ( Stenström et al. 2000), started 1 month prior to the beginning of the rut. Our time-lagged analysis showed that the peak of marking activities was reached 5 days prior to the peak of females’ arrival. In other words, everything is ready prior to the females’ arrival. Based on our on-field experience, we believe that high-ranking males in excellent body conditions would put any effort to mark the lek area prior to the females’ arrival, in the attempt to replace the other males’ marks as well as to produce several new ones (sensu Stenström et al. 2000). Therefore, an estrus female prior to approaching the lek would have the chance to smell the main scent along the way. Although this is a fascinating hypothesis on the secret of success of bucks in a fallow deer lek, it has yet to be tested.

(a) A fallow deer sore (2–3 y.o.) visiting the lek on 25 September 2007, that is, more than 1 week before females began visiting the mating site. An adult male (buck, age ≥ 4 y.o.) can be seen in the background (indicated by the arrow) while occupying and defending a lek territory (photo by G. Frescura). (b) Two fallow bucks pictured while fighting close to the lek area on 2 October 2004, few days before the first copulation observed (photo by B. Caleo).

(a) A fallow deer sore (2–3 y.o.) visiting the lek on 25 September 2007, that is, more than 1 week before females began visiting the mating site. An adult male (buck, age ≥ 4 y.o.) can be seen in the background (indicated by the arrow) while occupying and defending a lek territory (photo by G. Frescura). (b) Two fallow bucks pictured while fighting close to the lek area on 2 October 2004, few days before the first copulation observed (photo by B. Caleo).

We were able to prove that adult males with more conspicuous morphological traits can defend a lek territory for longer. Body mass is a key feature explaining territoriality in many lekking species, with heavy males being dominant in male–male interactions ( Balmford et al. 1992 McElligott et al. 2001). Heavy males are assumed to be better able to maintain their muscle stores and dominance than light males ( Bachman and Widemo 1999). In black grouse, dominance is largely determined by fighting success related to body mass ( Alatalo 1991). However, phenotypic data in our study case could not predict the highly skewed mating success recorded in a fallow deer lek yet again, we hope that further behavioral data collected prior to the mating season may contribute to the explanation of variability in mating success. Fiske et al. (1998) raised the concern that the sample sizes employed in most studies of leks have little power to detect a relationship between mating success and such exaggerated traits as body mass and antler length. Indeed, we acknowledge that our analyses with phenotypic data suffered from the small size of the sample compared with the analyses deploying age as main predictor.

Sexual selection is expected to be stronger in lekking species than in other ones ( Darwin 1871). In such a situation of intense intrasexual competition and markedly skewed male reproductive success ( Clutton-Brock et al. 1988), non-mating males appear to resort to alternative and less successful mating strategies ( Clutton-Brock et al. 1988 Ciuti et al. 2011). For instance, as most of the copulations take place in the leks ( Alatalo et al. 1992 Höglund and Alatalo 1995), yearling male black grouses schedule their reproductive effort differently from adult males in order to avoid competition ( Nieminen 2014). Such pattern has been found also in some nonlekking ungulates (e.g., Alpine chamois [ Mason et al. 2012], and red deer [ Mysterud et al. 2008]. Based on these studies, we wrongly predicted that, in our fallow deer lek, immature and/or less competitive males were supposed to leave later than successful males, in the attempt to mate when the latter were exhausted ( Preston et al. 2001 Mysterud et al. 2008), after roughly 2 months without feeding ( Apollonio and Di Vittorio 2004). During the last part of the rut, male–male competition can certainly be lower as a consequence of fatigue ( Stevenson and Bancroft 1995 Pelabon et al. 1999), but also because of the reduced number of females and males in the lek ( Apollonio et al. 1992) and in fact less competitive males left the lek earlier than the others. Arguably, the alternative strategy adopted by these unsuccessful males may be to leave the lek and follow the females leaving the area as well ( Clutton-Brock et al. 1988 Langbein and Thirgood 1989). Likewise, these males arrived at the lek almost simultaneously with the arrival of females. The presence of immature males in the lek ( Figure 5a) can be considered a chance for them to acquire experience on mating activities, which may be crucial during the following reproductive seasons ( Bekoff 1977 Byers 1980 Rothstein and Griswold 1991 Pelabon et al. 1999).

Why do bucks remain for such a long time in the lek after the last copulation? The majority of females showed up in the lek during a brief time window, that is, roughly 2 weeks, based on our telemetry data. However, females may return to the lek. Indeed, estrus in female fallow deer lasts less than 24h ( Chapman D and Chapman N 1997) and, if fertilization fails, they can have a second estrus after 28 days ( Chapman D and Chapman N 1997). Therefore, adult males remaining in the lek after the end of the rut may have the chance to mate with these females.

We described the timing of lek use in a lekking mammal and its link with mating success, and discussed similarities and differences with other lekking species, including birds. However, few studies have thoroughly investigated how pre-rut behaviors may affect mating success during the breeding season in lekking birds and mammals, and further work in this area is required.

Larynx descent in male and female deer - Biology


We can easily and reliably identify the gender of an unfamiliar interlocutor over the telephone. This is because our voice is “sexually dimorphic”: men typically speak with a lower fundamental frequency (F0 - lower pitch) and lower vocal tract resonances (ΔF – “deeper” timbre) than women. While the biological bases of these differences are well understood, and mostly down to size differences between men and women, very little is known about the extent to which we can play with these differences to accentuate or de-emphasise our perceived gender, masculinity and femininity in a range of social roles and contexts. The general aim of this thesis is to investigate the behavioural basis of gender expression in the human voice in both children and adults. More specifically, I hypothesise that, on top of the biologically determined sexual dimorphism, humans use a “gender code” consisting of vocal gestures (global F0 and ΔF adjustments) aimed at altering the gender attributes conveyed by their voice. In order to test this hypothesis, I first explore how acoustic variation of sexually dimorphic acoustic cues (F0 and ΔF) relates to physiological differences in pre-pubertal speakers (vocal tract length) and adult speakers (body height and salivary testosterone levels), and show that voice gender variation cannot be solely explained by static, biologically determined differences in vocal apparatus and body size of speakers. Subsequently, I show that both children and adult speakers can spontaneously modify their voice gender by lowering (raising) F0 and ΔF to masculinise (feminise) their voice, a key ability for the hypothesised control of voice gender. Finally, I investigate the interplay between voice gender expression and social context in relation to cultural stereotypes. I report that listeners spontaneously integrate stereotypical information in the auditory and visual domain to make stereotypical judgments about children’s gender and that adult actors manipulate their gender expression in line with stereotypical gendered notions of homosexuality. Overall, this corpus of data supports the existence of a “gender code” in human nonverbal vocal communication. This “gender code” provides not only a methodological framework with which to empirically investigate variation in voice gender and its role in expressing gender identity, but also a unifying theoretical structure to understand the origins of such variation from both evolutionary and social perspectives

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The Present Study

The present study is the first to test whether humans can modulate voice features known to be associated with body size (fundamental and formant frequencies) when instructed to deliberately alter their apparent body size. In addition, we examined whether this voice modulation reflects real (physical) and perceived relationships between the human voice and body (i.e., lower F0 and formants indicate larger size and visa versa), whether the behaviour differs between the sexes, and whether the behaviour is present cross-culturally.

We tested these hypotheses in 167 men and women from three distinct cultures and language groups: Canada (English), Cuba (Spanish), and Poland (Polish). Participants were recorded speaking vowel sounds in their baseline voice and while imitating a physically large and small body size. We predicted that participants would lower F0 and formants (increase apparent vocal tract length, VTL) to convey large size, and raise voice F0 and formants (reduce VTL) to convey small size. We further predicted that men would modulate their voices more than women, thereby accounting for some of the unexplained sexual dimorphism in F0 and formants. In contrast, we predicted that patterns of voice modulation would not differ across the three cultures. This latter finding would provide some support for fairly universal sound-size correspondences, and/or anatomical or biomechanical constraints on voice modulation.

The present study was specifically designed to test for the first time whether adult speakers are capable of volitional adjustments to their larynx (fundamental frequency modulation) and vocal tract (formant frequency modulation) in a manner that parallels the known relationships between these vocal parameters and body size in humans. Acoustic analyses were utilized to measure voice frequency parameters and to test whether these modulations exceed just-noticeable differences in F0 and formant perception. However in the present study we did not test whether these modulations effectively alter listeners’ perceptions of the vocalizer’s body size.

Biological Basis of Sex Appeal

For further readings, I suggest going to the Media and Communications Studies website.


All of the information in Part One applies to human reproductive strategy. Men are basically promiscuous women are basically selective. Male criteria are physical female criteria are physical and social. Men compete with each other for women's attention women select those men who win competitions. There are, however, major modifying factors in human strategy that make humans unique among the animals. The first is the human mind, which I will discuss later. The second is the human anatomy, equally unique, which I will discuss now.

Human anatomy differs rather radically from that of other mammals, in particular other primates. This difference has a major effect on how humans approach sex.

The biology, anatomy and physiology of most mammalian life on Earth lead to an instinctive approach. The biological imperatives guide male and female sexual behavior, and anatomy does nothing to impede that behavior. Note I say "most". There is one notable exception: human beings.

Typical land mammalian anatomical structure enhances rather than impedes reproduction.(8) For example, let's examine a typical female land mammal. She walks on all fours, her rear legs at right angles to her spine. Her vagina is under her tail and flush to the surface.

What these factors mean is significant. First, the male mounts from the rear for sexual intercourse. He approaches from the rear, places his weight on her back, and engages. The technical term for this is lordosis. (Beach, 1968 Morgan, 1972)

The position of her limbs makes it possible for her to support his weight during intercourse without a lot of effort. Her limbs don't impede intercourse. In addition, if she is not ready she can simply walk away.

The effort she must expend in intercourse is also reduced (remember how important her effort is biologically). She need only stand still and let him do the work.

Of course, animals don't engage in mating all the time. So for mammals, the vagina, a very delicate organ, is well protected by the tail or by the hip and leg structure. Nonetheless, during mating it is easily accessible.

Some of you may be thinking, "What has this to do with humans? Humans aren't built anything at all like deer or cows or horses. What about primates, which humans are like?"

Very well, what are primates like? Well, very much like deer or cows or horses. They primarily walk on all fours, males mount from the rear, her limbs can easily take his weight during intercourse and have great lateral flexibility. Her vagina is near the tail bone and on the surface, easily accessible to the male when she presents her posterior. The position of her limbs and a callosity on her rump also protect it when she sits. Thus, technique hasn't changed from deer to chimp.(9)

It is when we begin to examine human sexual anatomy that problems become apparent. The human body seems designed to impede rather than enhance intercourse.

Most of the differences between non-human and human anatomy that are important to this discussion are in the female structure. First, and most obvious, is the human upright stance. Only humans normally walk on their hind legs rather than on all fours and have the hip and leg structures that make it easy and natural. For males, this causes little in the way of problems since he's convex rather than concave.

For females, however, it is a major problem. As her legs rotated about her hips, moving from a right angle to in-line with her spine, her vaginal opening traveled farther and farther forward. Also, instead of being surface mounted, like other land mammals, her vagina retreated into her body with a covering of extra flesh. (Hamburg, 1974)

There were not only changes in the position of her vagina. Her legs changed radically as well from those of all other primates. First, her legs got closer and closer together. Second, her hip joints reformed to reduce lateral flexibility and stabilize her upright posture. Finally, instead of the spindly, bowed leg structure that all other primates had and have, her legs turned into long, thick, heavy, muscular columns.

A last major change in her anatomy was her buttocks. Unlike any other creature on earth, including the primates, humans have big buttocks, sometimes so large they form a shelf in the back. And it is almost axiomatic that no matter the race or culture, the female will have a bigger behind than the male.

At this point you may very well be asking yourself, "So what? So women have large buttocks -- so do men. So women walk upright -- so do men. What's the big deal?"

It's a good question. The answer is that as the female primate changed into the female human, her new body made sex difficult. Her vagina was now not easily accessible but difficult to get to. It moved far forward, got a covering layer of flesh, and became hidden between two heavy columns of bone and muscle.

"Nonsense!" you reply. "Where do all these babies come from, if sex is impossible? Men and women do get together, you know."

Indeed, they do, but not the way almost any other primate or land mammal does. Remember, all these changes in female anatomy occurred before humans became human. Let's examine what may have happened long ago and far away.

Ms. Primate, decked out in her new body, bounds up to a likely looking male and presents her posterior -- after all, land mammals mate from the rear. He, of course, responds. However, there is a new and frustrating development -- he can't reach. Equipped as he is with a primate penis, which is small,(10) her vagina is too far forward, her legs too close together, and her buttocks hold him too far away.

"Then the human race died out," you sneer sarcastically, knowing such is not the case. Obviously the human race did not die out. To avoid this fate, the male primate had two choices: evolve physically to compensate for her changes, or change his technique. In fact, the male did both.

First, the proto-human male evolved an over-sized penis, the largest in the primate world, and one of the largest in comparison to body size in nature.(11) However, since this evolution in male structure was in response to changes in the female, he was always a little behind (no pun intended).

It was his solution to this problem that has had a great influence on human male and female attitudes towards sex -- he changed his technique.

To understand the significance of his changing his technique, we must examinesome aspects of animal behavior, in particular aggression and appeasement. First, some definitions: what do I mean by aggression and appeasement. The modern definition of aggression is a cultural, rather than a biological one. Today, "aggression" means the deliberate infliction of harm on someone or something else. However, biological aggression is an organism's assertion of itself to gain survival or reproductive rights. Aggression can result in the infliction of harm on something else, but not necessarily. For example, the baboon male can assert itself simply by flashing its eyelids and yawning. He doesn't have to move at all, and no other baboon suffers the slightest physical harm (it may cause a certain loss of self-esteem for the other baboon, but nothing more). Only in extreme cases, such as the vicious mating fights of elephant seals (LeBoeuf, 1974), does physical chastisement that causes great injury to other members of the group occur.

Every animal, if it is to ensure that its genes get passed on, must have a degree of aggression. It must assert itself as the most deserving of procreation animals that do not assert themselves end themselves.

However, the aggression towards other members of an animal's own species is usually limited. For example, the males' mating battles may appear vicious and aimed at killing each other. True, the fight may severely injure one or both, and one or both may later die of his wounds or exhaustion. However, one actually killing the other during combat is rare.

In most instances, when one of the contenders has had enough, he will run away or make an appeasement signal. If he runs, the winner may chase him for a short distance, and then the battle is forgotten -- there are no grudges held (unless, of course, the loser comes back again and again, in which case the winner delivers a more definite lesson). If the loser makes an appeasement signal, it may be exposing the throat, lying down on his back, or otherwise exposing himself to a killing stroke from the winner. (Morgan, 1972) However, the killing stroke doesn't come -- the winner accepts the loser's capitulation and stops attacking.

The limits on aggression are instinctive and immediate a winner does not continue an attack after the loser submits or runs away, does not carry a grudge, does not try to gain revenge. Intraspecies aggression is to establish status, breeding rights, or to chastise improper behavior (that which may endanger the species). Once an animal submits, the aggressor stops the attack and backs off he or she has no choice -- an animal cannot fight instinct.

Such behavior is vital if a species is to avoid killing itself off. It is particularly important in those species that nature has equipped with deadly weapons such as long, pointy teeth and claws.

Now let's examine what all this means to Ms. and Mr. Protohuman. They, like other animals, must have had a degree of aggression to survive. Those that were most capable of wresting a living from the environment and procreating were the most successful.

Protohumans were undoubtedly as social as primates are today. (Leakey, 1977) Thus, they probably used aggression on each other to establish status, breeding rights, and to chastise.

The protohuman was small, perhaps no more than three and a half to four feet tall, (Leakey, 1977) and lacked much in the way of natural weapons. Thus, although they must have had aggression and appeasement signals like all animals, they were probably rather weak, strong signals only needed when one animal can easily kill another. Nonetheless, they must have been strong enough to avoid having one kill another through ignoring appeasement.

"What does all this have to do with the male changing his technique?" you may ask. Let's get back to the scenario and see what happens next.

She has presented her posterior and he tries to respond. However, her newly arranged and pneumatic body prevents his success. Now, what happens if some bright boy comes up with a flash of brilliance: "If I can't reach from this side, how about if I try from the other?" Carrying out his brilliant plan, he flips her on her back, spreads her legs, and tries again.

This is fine for him. However, what is her reaction? Remember, up to this time, all mating has been from the rear. For him to flip her on her back and get on top of her must mean, to her, that he is attacking, not mating. On her back her soft belly is unprotected, she can't run, her legs are unavailable since he's between them. In other words, she's scared out of her little protohuman mind.

She has two choices: fight back, or submit. If she fights back, he fights as well. Since he is probably bigger and stronger, if only slightly, he will probably win. She will thus fall back on choice two -- she submits and makes appeasement signals.

Now is when things get weird. She submits, making appropriate appeasement signals. He, following instinct triggered by her signals, immediately stops what he is doing and backs away. It doesn't matter that he wasn't actually attacking. What does matter is she made appeasement signals and he must back away.

She, of course, is bewildered. She was all set for the undoubtedly enjoyable activity of sex. Suddenly, he attacks her. What's the matter with him?

He's even more confused. She came up obviously prepared for fun. He was of like mind. However, he has difficulties because of her changed anatomy that he hasn't adapted to yet. He came up with the perfect solution, and she immediately tried to fight him off. What's the matter with her? Then, when she stopped fighting, he instantly lost interest. What's the matter with him? What's the matter with this whole business?

However, this was the story of Mr. A. What about Mr. B? Same scenario, but when she makes appeasement signals, Mr. B reacts. However, unlike Mr. A, he does not back off, but continues until orgasm. Why? His instinctual reaction to appeasement signals is weak they do not instantly turn off his actions. The upshot is Mr. A and his genes die out Mr. B and his genes continue. Enough Mr. Bs and the instinct for stopping aggressive behavior when opponents surrender is bred out of the species. Aggression is also bred into sex. This is not that unusual. For example, "The female blue heron hears the love screech of the male. She picks her heart's desire and settles on a branch nearby. The male immediately begins to court her. The moment she indicates interest and approaches him, though, he changes hismind, becomes unpleasant, shoos her away, or even attacks her. As soon as the discourage female flies off, he screeches after her. If she gives him another chance and flies back, he may very well attack her again. Gradually, though, should the female's patience last that long, the fickle male's grumpiness subsides and he may actually be ready to mate. He is conflicted and ambivalent. Sex and aggression are mixed up in his mind, and the confusion is so profound that, if not for the patience of the female, this species might fail to reproduce itself. But a similar confusion in the minds especially of males holds for many species, including reptiles, birds, and mammals. Some the the brain's neural circuitry for aggression seems dangerously cheek by jowl with the neural circuitry for sex. The resulting behavior is strangely familiar. But of course humans are not herons." (Sagan & Druyan, 1992, p. 191)

All this from human females standing up and growing buttocks? Yes. Why those features? There are many theories, many of which seem to say that females grew these and other features, such as breasts, ear lobes and plump lips to be more appealing to the males, to make sex sexier (most of these theories have been advanced by male anthropologists, such as Desmond Morris in his THE NAKED APE, an interesting point for speculation). I reply, hogwash. Evolution does not create major structural changes in animals to make them sexier and at the same time make sex more difficult physically, and by extension psychologically. Besides, what was wrong with the old features? Chimps and baboons still have them and they don't seem to find each other unattractive. Warthogs find other warthogs attractive without buttocks and large, well-rounded breasts, too.

No, evolution creates changes that improve chances for survival if the changes don't contribute to survival, the animal carrying them dies out. Why these changes occurred doesn't concern us, are a matter of controversy, and in any case would take too long to explain in an advertising book.(12) Suffice it to say, nature thought they were necessary to improve the female's, and by extension her offsprings', chance of survival.

However, convenience doesn't figure into evolution. An animal either adapts to the changes or dies out. Such is the case with protohumans, their anatomy and their sex lives -- the changes contributed to survival, they adapted to the inconvenience. That adaptation to inconvenience has guided human reproductive strategy, and scarred relations between the sexes, ever since. However, as long as babies are born, nature doesn't care.

The above is a look at the biology of human reproduction. However, as mentioned earlier, humans have something that no other animal has, and that has a greater effect on reproduction strategy than any other animal -- the human mind. I will discuss that in the next chapter, under REPRODUCTION AND SOCIETY.

8 Note that I refer to land mammals. There are, of course, aquatic mammals such as whales, dolphins and seals. However, since very little advertising is aimed at them, I will confine discussion to land mammals.

9 Gibbons, which hang by their arims during mating, mate face to face. Bonobos (pygmy chimps) also occasionally mae face to face, but the usual method is lordosis.

10 The gorilla's erect penis averages only 2 inches in length.

11 The flea has one 15 times his own body length, something that would give any man an inferiority complex.

12 If you're interested in one possible explanation, one that most anthropologists dismiss as untenable but is entertaining, see Elaine Morgan's THE DESCENT OF WOMAN. If nothing else, it avoid the underlying, subconscious male bias of many attempts to explain why humans are physically so different from other primates.
Return Go to Part One of Biological Basis of Sex Appeal

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Cognition and Behavioral Flexibility

While many mating preferences have a genetic basis, the question remains as to whether and how learning and/or experience can alter an individual’s mate choice decisions. The ability to learn from experience offers a certain degree of flexibility which is crucial to living in a variable, constantly changing environment (Dodson 1988). In this context, �havioral flexibility” denotes the ability to better adapt the own behavior to altered environmental conditions or unpredictable resources (Bond etਊl. 2007). It requires individuals to rapidly shift from a no longer viable strategy to a new one to obtain new associations as environmental demands change (Rayburn-Reeves etਊl. 2017a,b). Therefore, assessing an individual’s behavioral flexibility allows to indirectly examine its level of 𠇌ognitive flexibility”. Cognitive flexibility has been defined as the ability to channelize attention between different tasks, for instance, in response to an alteration of rules or demands (Scott 1962). Accordingly, it is the aptitude to adapt the own rational to new situations and/or to overcome the habitual thinking and decision-making processes (Deak 2003 Moore and Malinowski 2009 Rayburn-Reeves etਊl. 2017a,b).

In several mammalian, avian and fish species, females were observed to show a higher performance than males in tasks requiring cognitive flexibility such as the discrimination reversal learning. For instance, female guppies appeared to be more innovative and interested in problem solving when given a novel foraging task involving spatial exploration (Laland and Reader 1999). Likewise, females solved learning flexibility tasks faster compared with their male conspecifics. In these studies, individuals were challenged either with a detour reaching task to join a group of conspecifics (Lucon-Xiccato and Bisazza 2017) or with a series of color discrimination reversal learning tasks (Lucon-Xiccato and Bisazza 2014).

To widen our understanding of the ways in which learning, other neurobiological aspects, and mate choice interact, coincide or differ between males and females within or between species, the topical collection of this Special Issue comprises a number of exciting contributions: Keagy etਊl. (2019) observed cognitive sex differences and their relationship to male mate choice. To do so, they repeatedly presented male and female three-spined sticklebacks Gasterosteus aculeatus with a detour task to assess initial inhibitory control and improvement over time, and examined, whether male mate choice was associated with female inhibitory control. Since males consistently outperformed females, there seemed to be suggestive evidence that males learned the task better than their conspecific females, although sex-specific differences in neophobia played an important role as well. Rystrom etਊl. (2019) have examined the flip side of the same coin. They challenged female three-spined sticklebacks with a dichotomous mate choice task using computer-animated males differing in breeding coloration. They examined their results with regard to the females’ spatial learning and reversal learning ability and possible correlations between an individual’s spatial learning ability and its mate assessment. Females spending more time to evaluate potential partners in a dichotomous mate choice task made fewer errors during both the initial and reverse spatial learning task. However, these females made more consecutive errors at the very beginning of the reversal phase, indicating that they were not quickly adapting to environmental changes, but quickly forming strict routines during the learning tasks.

Plath etਊl. (2019) have also focused on mate assessment to which they added the exciting aspect of the attendances or absences of predators. They assigned wild-caught (predator-experienced) and laboratory-reared (predator-naïve) Western mosquitofish G. affinis to 2 mate choice tests, during one of which different animated pre-dators were present. They aimed to investigate whether (innate) mating preferences would change under immediate predation threat and whether potential predator-induced changes in mating preferences would differ between sexes or depend on the choosing individual’s personality and/or body size. Wild-caught fish altered their mate choice decisions most when exposed to co-occurring predators whereas laboratory-reared individuals responded most to coevolved predators, suggesting that both innate mechanisms and learning effects were involved. The effects were stronger in bolder individuals, likely because those phenotypes face an overall increased predation risk.

Within the scope of this Special Issue, sex-specific differences, visual discrimination ability, and aspects of spatial orientation, although in different contexts have been studied in túngara frogs and 3 poeciliid species. Ventura etਊl. (2019) tested male and female túngara frogs for their place learning capabilities by using a 2-arm maze featuring 2 differently marked doors (red, yellow, or achromatic cues), one of which was rewarded with return to the home cage. They examined whether the type of door marking (chromatic or achromatic) had a sex-specific effect on the individuals’ place learning behavior. Frogs rewarded to choose the yellow door showed an increase in correct choices and an increased preference for the yellow door in the course of training. However, authors found no evidence for a sex difference in learning. Fuss and Witte (2019) performed one of the first comparative studies dealing with behavioral flexibility in the context of (cognitive) sex-specific differences in 3 related poeciliid species (P. latipinna, P. mexicana, and P. reticulata). They assessed male and female individuals for their ability to exploit previously gained knowledge using a simple color discrimination paradigm (red, yellow, or green cues) and, subsequently, for their behavioral flexibility in a series of reversal tasks. While no sex differences were observed in sailfin mollies, male Atlantic mollies learned to solve the initial color discrimination task significantly faster than their conspecific females. Surprisingly and contrasting our expectations of a reflection of the results of a previous study on guppies (Lucon-Xiccato and Bisazza 2014), only females solved the initial task in our study, whereas males failed to learn any of the tasks they were assigned to. Regarding the expected sex differences in accuracy and behavioral flexibility during serial reversal learning, different results for the 3 species under investigation were observed. Compared with previous studies or other vertebrate taxa, the hitherto apparently universal pattern (i.e., females showing higher behavioral flexibility) seemed to be inverted in the 2 examined molly species.

Animal Diversity Web

Odocoileus hemionus occurs over most of North America west of the 100th meridian from 23 degrees to 60 degrees N. The eastern edge of the usual range extends from southwestern Saskatchewan through central North and South Dakota, Nebraska, Kansas, and western Texas. Isolated occurrences have been reported from Minnesota, Iowa, and Missouri. Major gaps in geographic distribution are in southern Nevada, southeastern California, southwestern Arizona, and the Great Salt Lake desert region. Apart from these gaps, O. hemionus occurs in all of the biomes of western North America north of central Mexico, except the Arctic tundra (Anderson 1984).


Odocoileus hemionus is remarkably adaptable. Of at least sixty types of natural vegetation west of the 100th meridian in the United States, all but two or three are or once were occupied by O. hemionus . Several additional vegetation types are inhabited in Canada and Mexico as well. The vegetation types in Mexico are similar to the types occurring in the United States. However, the tropical deciduous vegetation at the tip of Baja California is unique. In Canada, O. hemionus occupies five boreal forest types that do not occur in the United States. O. hemionus occupies a wide range of habitat provinces (regions of land containing particular vegetation types) in western North America. These habitat provinces include the California woodland chaparral, the Mojave Sonoran desert, the Interior semidesert shrub woodland, the Great Plains, the Colorado Plateau shrubland and forest, the Great Basin, the Sagebrush steepe, the Northern mountain, and the Canadian boreal forest (Wallmo 1981).

Physical Description

The pelage of Odocoileus hemionus ranges from dark brown gray, dark and light ash-gray to brown and even reddish. The rump patch may be white or yellow, while the throat patch is white (Geist 1981). The white tails of most mule deer terminate in a tuft of black hairs, or less commonly in a thin tuft of white hairs. On some mule deer, a dark dorsal line runs from the back, down the top of the tail, to the black tail tip. All markings vary considerably among O. hemionus , but remain constant throughout the life of an individual. O. hemionus possess a dark V-shaped mark, extending from a point between the eyes upward and laterally. This mark is more conspicuous in males. Growth in O. hemionus during the first year is roughly parallel in males and females. Thereafter, males, in general, exceed females in carcass weight, chest girth, neck circumference, body length, head length, cranial breadth, shoulder height, hindfoot length, and hoof length (Anderson 1984). Carcass weight ranges from 45 to 150 kg in males, and 43 to 75 kg in females. Chest girth ranges from 80 to 117 cm in males, and 78 to 97 cm in females. Neck circumference ranges from 30 to 65 cm in males, and 26 to 38 cm in females. Body length ranges from 126 to 168 cm in males, and 125 to 156 cm in females. Head length ranges from 28 to 35 cm in males, and 27 to 33 cm in females. Cranial breadth ranges from 11 to 16 cm in males, and 10 to 14 cm in females. Shoulder height ranges from 84 to 106 cm in males, and 80 to 100 cm in females (Wallmo 1981).


Odocoileus hemionus is a polygynous species, having a tending-bond type breeding system. Courtship and mating occur within the group (Geist 1981). A dominant male tends an estrus female until mating or displacement by another male occurs. Dominance is largely a function of size, with the largest males, which possess the largest antlers, performing most of the copulations (Kucera 1978). Most O. hemionus females conceive during their second year and only rarely during their first year. The breeding peak in O. hemionus occurs mainly from late November through mid-December. The average gestation length is 204 days. The peak birth period in O. hemionus is estimated to be from June 16th to July 6th, with most births occurring in June. The time of birth varies according to the environment. Robinette (1977) calculated that a 305-m rise in elevation is associated with a 7-day delay in the birth period. The mass at birth of O. hemionus ranges from 2 to 5 kg. Mass at birth is affected by litter size and sex, with males being heavier. The common liter size is two, with mothers in their first or second breeding year most frequently producing singletons. Weaning begins at about 5 weeks of age and usually is completed at age 16 weeks. Full development of most skeletal attributes occurs at about 49 months of age in males and 37 months of age in females. However, gains in carcass mass are continuous until an age of 120 months in males and 96 months in females. In O. hemionus , male neonates predominate when poor nutrition prevails about 6 weeks before, and during, the breeding period. Ovulation in female O. hemionus occurs about 12 to 14 hours after estrus terminates. Approximately 27 to 29 days elapse between conception and implantation in female O. hemionus . Among male O. hemionus , testicular mass and volume are maximal during November and minimal during April and May (Anderson 1984).

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring 1.5 AnAge
  • Average gestation period 207 days AnAge
  • Average age at sexual or reproductive maturity (female)
    Sex: female 478 days AnAge
  • Average age at sexual or reproductive maturity (male)
    Sex: male 503 days AnAge



Individuals of Odocoileus hemionus tend to confine their daily movements to discrete home ranges. Most mule deer with established home ranges use the same winter and summer home ranges in consecutive years. Dispersal in O. hemionus involves movements beyond the home range to distances of up to 8 km. This movement results in the establishment of a new home range. Seasonal movements involving migrations from higher elevations (summer ranges) to lower winter ranges are associated, in part, with decreasing temperatures, severe snowstorms, and snow depths that reduce mobility and food supply. Deep snows ultimately limit useable range to a fraction of the total. Mule deer in the arid southwest may migrate in response to rainfall patterns. Common predators of O. hemionus include pumas, coyotes, bobcats, golden eagles, feral dogs, and black bears. The social system of O. hemionus consists of clans of females related by maternal descent. These clans are the facultative resource defenders. Males disperse as individuals or aggregate in groups of unrelated individuals. During winter and spring, the stability of female clans and male groups is maintained with dominance hierarchies. Increases in strife and alarm behavior, and decreases in play among fawns, occur as population density increases. The frequency of aggressive behavior between the sexes remains low year round in O. hemionus . Communication among O. hemionus is facilitated by the sebaceous and sudoriferous secretory cells of five integumentary glands. The cells of each gland produce specific scents (pheromones) that elicit specific reactions in conspecifics. The metatarsal gland produces an alarm pheromone, the tarsal gland aids in mutual recognition, the interdigital gland leaves a scent trail, and the function of the tail gland is unknown. Urine has a pheromone function at all ages and for both sexes. It is deposited on tufts of hair surrounding the tarsal glands. In fawns, it functions as a distress signal, while in adults, it functions as a threat signal (Anderson 1984). O. hemionus has several distinct strategies for avoiding predators. O. hemionus specializes in detecting danger at a very long range by means of large ears and excellent vision. Males can quickly detect and visually track another animal as far as 600 meters. Once danger is detected, O. hemionus may choose to hide, or move into cover and cautiously outmaneuver the predator. Another strategy is to depart while the predator is still a long way off and move several miles to another area. O. hemionus , instead, may bound rapidly uphill, imposing on pursuing predators an unacceptably high cost per unit time of locomotion. In yet another strategy, O. hemionus may bound off and then trot away, stopping frequently to gain information on the disturbance. This initial bounding, combined with release of metatarsal scent that inhibits feeding, is highly advantageous in that, by alarming others, it causes other mule deer to bound off as well, reducing the conspicuousness of the deer who bounded off first. This strategy would also trigger group formation. Finally, when a predator closes in, O. hemionus initiates evasive maneuvers based on sudden unpredictable changes in direction and on placing obstacles between itself and the predator. This strategy, however, does not work against group-hunting predators. O. hemionus is an excellent swimmer, but water is rarely used as a means of escaping predators (Geist).

Communication and Perception

Food Habits

Odocoileus hemionus is a small ruminant with limited ability to digest highly fibrous roughage (Short 1981). Optimum growth and productivity of individuals and populations are dependent upon adequate supplies of highly digestible, succulent forage. Diets consisting primarily of woody twigs cannot meet the maintenance requirements of O. hemionus . Based on its stomach structure and its diet of woody and herbaceous forage in approximate equal proportions, O. hemionus is classified as an intermediate feeder. Because nutritious forage is in poor supply for much of the year, O hemionus has an annual cycle of metabolic rates. A higher energy flux and food intake in the summer enables O. hemionus to capitalize on abundant high-quality forage for growth and fat storage. A lower energy flux in the winter permits O. hemionus to survive on a lower intake of poor-quality forage while minimizing the catabolism of stored fat for body functions. The estimated rate of food intake is about 22 g/kg body weight/day. In adult males, food intake drops abruptly with the onset of rut (Anderson 1984). O. hemionus frequently browses leaves and twigs of trees and shrubs. Green leaves are very succulent and, except for epidermal tissue and structural ribs, consist largely of easily digestible cell contents. Dead and weathered leaves have little protein and high cell-wall values. As a result, they are of very low digestibility. O. hemionus also eats acorns, legume seeds, and fleshy fruits, including berries and drupes, that have moderate cell-wall levels and are easily digested (Short 1981).

Economic Importance for Humans: Positive

Odocoileus hemionus is of tremendous interest to hunters. Populations of O. hemionus that are large enough to support hunting during two or three weeks in autumn offer countless recreational opportunities for the public. This desire to hunt generates revenue for the economy (Wallmo 1981).

Economic Importance for Humans: Negative

Douglas fir and Ponderosa pine are of major economic importance for commercial timber. However, these trees are browsed heavily by O. hemionus . Browsing of other trees is seldom considered an economic problem. In the Douglas fir region, O. hemionus browses on trees during both the dormant and growing seasons. Practices that encourage the growth of O. hemionus populations can therefore also encourage damage. Douglas fir is harvested mainly by clearcutting and is regenerated by planting with nursery-grown stock. O. hemionus is attracted to clear-cuts, and Douglas fir is an acceptable and sometimes preferred forage species. This situation invites browsing of sufficient intensity to influence forest regeneration in many areas (Wallmo 1981).

Conservation Status

All federal, state, and provincial land and wildlife management agencies recognize the fundamental need to maintain O. hemionus ranges and keep them habitable. To counter the trend of agricultural development, rangeland conversion, mining, road and highway construction, and the development of housing tracts, many states and provinces have purchased critical areas, especially winter ranges, to maintain the various habitats of O. hemionus . But, due to political opposition to government acquisition of privately owned lands, plus a scarcity of funds for this purpose, only a small fraction of O. hemionus ranges has been acquired by the government. The effects of reduced O. hemionus ranges can be mitigated by better management of the remaining lands to maximize their productiviy for O. hemionus . Various habitat management programs include the manipulation of livestock grazing, the manipulation of cultivative communities, and the manipulation of vegetative communities. For O. hemionus , the optimal successional stages are subclimax plant communities that can be perpetuated only through the influence of humans. Since O. hemionus production is not the primary management goal on most private or public lands in western North America, O. hemionus habitat improvement programs typically involve a complex process of coordination among bureaucracies with missions that are usually not compatible (Wallmo 1981).

Other Comments

The annual cycle of antler growth in O. hemionus is initiated and controlled by changes in day length acting on several cell types of the anterior pituitary. These cell types secrete growth-stimulating hormones that act mainly on the antlers and incidentally on the testes. Antler hardening, shedding, and the breeding period are mediated by decreasing day length through the action of gonadotropins on Leydig cells, thus producing androgens. Androgens induce secondary ossification, accelerate maturation, induce behavioral changes that result in shedding antler velvet, and aid in the maintenance of osteoblasts and osteocytes to maintain antlers in hard bone condition. Withdrawal of androgens at the end of the breeding season permits resorption of bone at the pedicel-antler junction and antler shedding. O. hemionus has excellent binocular vision. While unable to detect motionless objects, O. hemionus is extraordinarily sensitive to moving objects. The sense of hearing is also extremely acute. O. hemionus is a target for various viral, bacterial, and parasitic diseases. For example, heavy amounts of gastrointestinal nematodes may cause death in O. hemionus . This parasitic disease is usually indicative of such predisposing factors as high mule deer density and malnutrition. Infection by the parasitic meningeal worm can cause fatal neurologic disease in O. hemionus . Livestock may transmit viral diseases to O. hemionus as seen in foot-and-mouth disease. This infection is characterized by blisters in the mouth, above the hooves, and between the digits (Anderson 1984).


Michael Misuraca (author), University of Michigan-Ann Arbor.


living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

uses smells or other chemicals to communicate

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor the fossil record does not distinguish these possibilities. Convergent in birds.

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

having the capacity to move from one place to another.

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

the area in which the animal is naturally found, the region in which it is endemic.

reproduction that includes combining the genetic contribution of two individuals, a male and a female

associates with others of its species forms social groups.

uses touch to communicate

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.


Geist, V. 1981. Behavior: adaptive strategies in mule deer. Pp. 157-224, in Mule and Black-tailed deer of North America (O. C. Wallmo, ed.). Univ. Nebraska Press, Lincoln, xvii + 605 pp.

Kucera, T. E. 1978. Social behavior and breeding system of the Desert mule deer. J. Mamm., 59:463-476.

Short, H.L. 1981. Nutrition and metabolism. Pp. 99-127, in Mule and Black-tailed deer of North America (O. C. Wallmo, ed.). Univ. Nebraska Press, Lincoln, xvii + 605 pp.

Wallmo, O. C. 1981. Mule and Black-tailed deer distribution and habitats. Pp. 1-25, in Mule and Black-tailed deer of North America (O. C. Wallmo, ed.). Univ. Nebraska Press, Lincoln, xvii + 605 pp.

Watch the video: different behaviors in male u0026 female deer? (August 2022).