Quality prevails over identity in the sexually selected vocalisations of an ageing mammal

BACKGROUND: Male sexually selected vocalisations generally contain both individuality and quality cues that are crucial in intra- as well as inter-sexual communication. As individuality is a fixed feature whereas male phenotypic quality changes with age, individuality and quality cues may be subjected to different selection pressures over time. Individuality (for example, morphology of the vocal apparatus) and quality (for example, body size and dominance status) can both affect the vocal production mechanism, inducing the same components of vocalisations to convey both kinds of information. In this case, do quality-related changes to the acoustic structure of calls induce a modification of vocal cues to identity from year to year? We investigated this question in fallow deer (Dama dama), in which some acoustic parameters of vocalisations (groans) code for both individuality and quality. RESULTS: We carried out a longitudinal analysis of groan individuality, examining the effects of age and dominance rank on the acoustic structure of groans of the same males recorded during consecutive years. We found both age- and rank-related changes to groans; the minimum values of the highest formant frequencies and the fundamental frequency increased with the age of males and they decreased when males became more dominant. Both age- and rank-related acoustic parameters contributed to individuality. Male quality changed with age, inducing a change in quality-related parameters and thus, a modification of vocal cues to male individuality between years. CONCLUSIONS: The encoding of individuality and quality information in the same components of vocalisations induces a tradeoff between these two kinds of signals over time. Fallow deer vocalisations are honest signals of quality that are not fixed over time but are modified dynamically according to male quality. As they are more reliable cues to quality than to individuality, they may not be used by conspecifics to recognize a given male from one year to another, but potentially used by both sexes to assess male quality during each breeding season

Mother-Young Recognition in an Ungulate Hider Species: A Unidirectional Proce

Parent‐offspring recognition is usually crucial for survival of young. In mammals, olfaction often only permits identification at short range, and vocalizations are important at longer distances. Following and hiding antipredator strategies found in newborn mammals may also affect parental recognition mechanisms. We investigated mother‐offspring recognition in fallow deer, an ungulate hider species. We analyzed the structure of adult female and fawn contact calls to determine whether they are individually distinctive and tested for mother‐offspring recognition. Only females (and not fawns) have individualized vocalizations, with the fundamental frequency as the most distinctive parameter. Playback experiments showed that fawns can distinguish the calls of their mothers from those of other females, but mothers could not discriminate their own and alien fawn calls. Thus, the vocal identification process is unidirectional. In followers, mother‐offspring acoustic recognition is mutual, and therefore the different antipredator strategies of newborn mammals may have shaped the modalities of parent‐offspring acoustic recognition

Mother-Young Recognition in an Ungulate Hider Species: A Unidirectional Proce

Parent‐offspring recognition is usually crucial for survival of young. In mammals, olfaction often only permits identification at short range, and vocalizations are important at longer distances. Following and hiding antipredator strategies found in newborn mammals may also affect parental recognition mechanisms. We investigated mother‐offspring recognition in fallow deer, an ungulate hider species. We analyzed the structure of adult female and fawn contact calls to determine whether they are individually distinctive and tested for mother‐offspring recognition. Only females (and not fawns) have individualized vocalizations, with the fundamental frequency as the most distinctive parameter. Playback experiments showed that fawns can distinguish the calls of their mothers from those of other females, but mothers could not discriminate their own and alien fawn calls. Thus, the vocal identification process is unidirectional. In followers, mother‐offspring acoustic recognition is mutual, and therefore the different antipredator strategies of newborn mammals may have shaped the modalities of parent‐offspring acoustic recognition

Fallow bucks attend to vocal cues of motivation and fatigue

Breeding vocalizations can provide up-to-date information about callers. During the rut, fallow buck calling rates vary in response to their nearest neighbors, and vocal fatigue is linked to body condition loss. We found that fallow bucks perceive higher calling rates as a greater threat and that bucks were sensitive to declines in the quality of the calls of other males. Over the breeding season, fallow bucks gain information from changing calls to continually assess the condition and motivation of conspecific

Learning and memory with neuropathic pain: impact of old age and progranulin deficiency

Persistent neuropathic pain is a frequent consequence of peripheral nerve injuries, particularly in the elderly. Using the IntelliCage we studied if sciatic nerve injury obstructed learning and memory in young and aged mice, each in wild type and progranulin deficient mice, which develop premature signs of brain aging. Both young and aged mice developed long-term nerve injury-evoked hyperalgesia and allodynia. In both genotypes, aged mice with neuropathic pain showed high error rates in place avoidance acquisition tasks. However, once learnt, these aged mice with neuropathic pain showed a significantly stronger maintenance of the aversive memory. Nerve injury did not affect place preference behavior in neither genotype, neither in young nor aged mice. However, nerve injury in progranulin deficient mice impaired the learning of spatial sequences of awarded places, particularly in the aged mice. This task required a discrimination of clockwise and anti-clockwise sequences. The chaining failure occurred only in progranulin deficient mice after nerve injury, but not in sham operated or wildtype mice, suggesting that progranulin was particularly important for compensatory adaptations after nerve injury. In contrast, all aged mice with neuropathic pain, irrespective of the genotype, had a long maintenance of aversive memory suggesting a negative alliance and possibly mutual aggravation of chronic neuropathic pain and aversive memory at old age

Early behavioural changes in mice infected with BSE and scrapie: automated home cage monitoring reveals prion strain differences.

Abstract Mice inoculated with transmissible spongiform encephalopathies (TSE) show behavioural abnormalities well before the appearance of clinical signs. TSE strains are obtained by serial re-infection of infectious brain homogenates in laboratory rodents. They are characterized by strain-typical brain lesion pro®les, which implies that they might be differentiated behaviourally as well. Seventy female C57BL/6 mice were tested, 14 per group. Controls received no or sham inocula, two other groups received scrapie strains adapted to mice (139A, ME7) and one group a mouse-adapted BSE strain (301C). From week 7 until the end of the incubation period, 8 mice per group were subjected once every 2 weeks to open-®eld and hot-plate tests. Assessment of clinical signs, and measuring of body weight, food and water consumption were carried out weekly on the remaining animals kept in single cages. In addition, locomotor activity was recorded continuously in these mice by means of infrared detectors. Monitoring of circadian activity revealed early signi®cant TSE strain differences, most pronounced during the nocturnal active phase. Behavioural changes in open-®eld tests also occurred before the appearance of clinical signs, and differences in rearing, wall rearing and snif®ng were strain-speci®c, however, such differences varied according to the period of testing. Hind paw lick latencies increased equally in all groups after week 19, jump latencies also increased in the two scrapie groups but not in the BSE group. It was at this time that clinical signs ®rst appeared consisting of ataxia, lack of balance, motor dyscoordination, and lordosis. These data imply that automated assessment of circadian activity in mice is a powerful and economical tool for early behavioural typing of TSE strains

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

The negative relationship between F0min and dominance rank (log-transformed).

<p>Lower values of dominance rank indicate higher ranking males. Higher ranking males produced groans with lower minimum fundamental frequency.</p

The negative relationships between body size and minimum formant dispersion (Dfmin).

<p>Bigger males emit groans characterised by lower minimum formant dispersion.</p