20 research outputs found
Low Frequency Groans Indicate Larger and More Dominant Fallow Deer (Dama dama) Males
Background: Models of honest advertisement predict that sexually selected calls should signal male quality. In most vertebrates, high quality males have larger body sizes that determine higher social status and in turn higher reproductive success. Previous research has emphasised the importance of vocal tract resonances or formant frequencies of calls as cues to body size in mammals. However, the role of the acoustic features of vocalisations as cues to other quality-related phenotypic characteristics of callers has rarely been investigated. Methodology/Principal Findings: We examined whether the acoustic structure of fallow deer groans provides reliable information on the quality of the caller, by exploring the relationships between male quality (body size, dominance rank, and mating success) and the frequency components of calls (fundamental frequency, formant frequencies, and formant dispersion). We found that body size was not related to the fundamental frequency of groans, whereas larger males produced groans with lower formant frequencies and lower formant dispersion. Groans of high-ranking males were characterised by lower minimum fundamental frequencies and to a lesser extent, by lower formant dispersions. Dominance rank was the factor most strongly related to mating success, with higher-ranking males having higher mating success. The minimum fundamental frequency and the minimum formant dispersion were indirectly related to male mating success (through dominance rank). Conclusion/Significance: Our study is the first to show that sexually selected vocalisations can signal social dominance in mammals other than primates, and reveals that independent acoustic components encode accurate information on different phenotypic aspects of male quality
Mating tactics of male feral goats (Capra hircus): risks and benefits.
Intense competition between males for reproduction has led to the evolution of alternative mating tactics (AMTs). Feral goat males usually use a tactic called tending, in which they defend oestrous females from other
males. Males may also use a second mating tactic called coursing, in which they gain access to oestrous females by disturbing a tending pair. Herein, we examine estimated
mating success (EMS) and risks of using these tactics. Tending was only used by mature (≥4 years old), higherranking males and accounted for 75% of EMS. Coursing was used by males of all ages and dominance ranks, and accounted for 25% of EMS. Using coursing, male kids
achieved 8% of EMS. Mature males achieved 92% of EMS. Both age and dominance rank were related to EMS, but age was not important after its relationship with dominance was controlled. Tending bouts were, on average, ca. 30 min long, while coursing bouts only averaged ca. 2 min. Males were more likely to suffer a butt while coursing than while tending, and formerly tending males were responsible for most butts. Kids that coursed had the highest risk of being butted. In most AMTs, there are reductions in the risks in relation to low fitness benefits. However, we found that the risks of butts during coursing were high, while our evidence suggests that the EMS was probably low. Nevertheless,
the existence of an effective AMT in male feral goats may have an important influence on the intensity of sexual selection and the effective population size
Noradrenergic Synaptic Function in the Bed Nucleus of the Stria Terminalis Varies in Animal Models of Anxiety and Addiction
Lewis rats show increased anxiety-like behaviors and drug consumption compared with Sprague-Dawley rats. Prior work suggests norepinephrine (NE) signaling in the bed nucleus of the stria terminalis (BNST) could have a role in mediating these phenotypes. Here, we investigated NE content and dynamics in the ventral BNST (vBNST) using fast-scan cyclic voltammetry in these two rat strains. We found that NE release evoked by electrical stimulus and its subsequent uptake was dysregulated in the more anxious Lewis rats. Because addiction is a multifaceted disease influenced by both genetic and environmental factors, we hypothesized NE dynamics would vary in these strains after the induction of a physical dependence on morphine. Following naloxone-precipitated morphine withdrawal, NE release and uptake dynamics were not changed in Lewis rats but were significantly altered in Sprague-Dawley rats. The alterations in Sprague-Dawley rats were accompanied by an increase in anxiety-like behavior in those animals as measured with the elevated plus maze. These studies suggest novel mechanisms involved in the development of affective disorders, and highlight the noradrenergic system in the vBNST as a common substrate for the manifestation of pathological anxiety and addiction
Male ruff colour as a rank signal in a monomorphic-horned mammal: behavioural correlates
Coexistence of individuals within a social group is
possible through the establishment of a hierarchy. Social dominance
is achieved through aggressive interactions, and, in
wild sheep and goats, it is related mainly to age, body size
and weapon size as rank signals. Adult male Himalayan tahr
are much larger than females and subadult males. They have a
prominent neck ruff, ranging in colour from yellow (5.5–
9.5 years old, i.e. young adults, golden males) to brown
(7.5–14.5 years old, i.e. older individuals, pale and dark
brown males), with golden males being the most dominant.
We investigated the social behaviour of male tahr and
analysed the relationships between ruff colour, courtship and
agonistic behaviour patterns during the rut. Colour classes
varied in their use of several behaviour patterns (male dominance:
approach, stare, horning vegetation; courtship: low
stretch, naso-genital contact, rush). Golden-ruffed males used
more threats than darker ones. Pale brown and dark brown
males addressed threats significantly more often to males of
lower or their own colour classes, respectively, whereas golden
ones addressed threats to all colour classes, including their
own. The courtship of dominant males was characterised by
the assertive rush, whereas that of subordinates did not. Ruff
colour of male Himalayan tahr may have evolved as a rank
signal, homologous to horn size in wild sheep and goats