• Body size and sexual selection in the koala

      Ellis, William A.; Bercovitch, Fred B. (2011)
      ...Koalas are sexually dimorphic in multiple domains, yet are absent from the literature on sexual selection and the structure of their mating system is unclear. We provide the first documentation of the strength of sexual selection in koalas by using microsatellite markers to identify sires....
    • Conspecific attraction

      Swaisgood, Ronald R.; Mills, D.S.; Marchant-Forde, J.N.; McGreevy, P.D.; Morton, D.B.; Nicol, C.J.; Phillips, C.J.C.; Sandoe, P.; Swaisgood, Ronald R. (CABICambridge, MA, 2010)
    • Deciphering genetic mate choice: Not so simple in group-housed conservation breeding programs

      Farquharson, Katherine A.; Hogg, Carolyn J.; Belov, Katherine; Grueber, Catherine E. (2020)
      Incorporating mate choice into conservation breeding programs can improve reproduction and the retention of natural behaviors. However, different types of genetic-based mate choice can have varied consequences for genetic diversity management. As a result, it is important to examine mechanisms of mate choice in captivity to assess its costs and benefits. Most research in this area has focused on experimental pairing trials; however, this resource-intensive approach is not always feasible in captive settings and can interfere with other management constraints. We used generalized linear mixed models and permutation approaches to investigate overall breeding success in group-housed Tasmanian devils at three nonmutually exclusive mate choice hypotheses: (a) advantage of heterozygous individuals, (b) advantage of dissimilar mates, and (c) optimum genetic distance, using both 1,948 genome-wide SNPs and 12 MHC-linked microsatellites. The managed devil insurance population is the largest such breeding program in Australia and is known to have high variance in reproductive success. We found that nongenetic factors such as age were the best predictors of breeding success in a competitive breeding scenario, with younger females and older males being more successful. We found no evidence of mate choice under the hypotheses tested. Mate choice varies among species and across environments, so we advocate for more studies in realistic captive management contexts as experimental or wild studies may not apply. Conservation managers must weigh up the need to wait for adequate sample sizes to detect mate choice with the risk that genetic changes may occur during this time in captivity. Our study shows that examining and integrating mate choice into the captive management of species housed in realistic, semi-natural group-based contexts may be more difficult than previously considered.
    • Demographic, environmental and genetic determinants of mating success in captive koalas (Phascolarctos cinereus)

      Abts, Kendra C.; Ivy, Jamie A.; DeWoody, J. Andrew (2018)
      Many factors have been shown to affect mating behavior. For instance, genes of the major histocompatibility complex (MHC) are known to influence mate choice in a wide variety of vertebrate species....
    • Disentangling the mechanisms of mate choice in a captive koala population

      Brandies, Parice A.; Grueber, Catherine E.; Ivy, Jamie A.; Hogg, Carolyn J.; Belov, Katherine (2018)
      Successful captive breeding programs are crucial to the long-term survival of many threatened species. However, pair incompatibility (breeding failure) limits sustainability of many captive populations. Understanding whether the drivers of this incompatibility are behavioral, genetic, or a combination of both, is crucial to improving breeding programs. We used 28 years of pairing data from the San Diego Zoo koala colony, plus genetic analyses using both major histocompatibility complex (MHC)-linked and non-MHC-linked microsatellite markers, to show that both genetic and non-genetic factors can influence mating success. Male age was reconfirmed to be a contributing factor to the likelihood of a koala pair copulating. This trend could also be related to a pair’s age difference, which was highly correlated with male age in our dataset. Familiarity was reconfirmed to increase the probability of a successful copulation. Our data provided evidence that females select mates based on MHC and genome-wide similarity. Male heterozygosity at MHC class II loci was associated with both pre- and post-copulatory female choice. Genome-wide similarity, and similarity at the MHC class II DAB locus, were also associated with female choice at the post-copulatory level. Finally, certain MHC-linked alleles were associated with either increased or decreased mating success. We predict that utilizing a variety of behavioral and MHC-dependent mate choice mechanisms improves female fitness through increased reproductive success. This study highlights the complexity of mate choice mechanisms in a species, and the importance of ascertaining mate choice mechanisms to improve the success of captive breeding programs.
    • Effects of combination birth control on estrous behavior in captive western lowland gorillas, Gorilla gorilla gorilla

      Sarfaty, A.; Margulis, S.W.; Atsalis, Sylvia (2012)
      Combination birth control pills (CBC) are one of the most common birth control methods used for western lowland gorillas (Gorilla gorilla gorilla) housed in zoos. Since zoos are interested in maintaining as many natural behaviors as possible, it is important to know how contraception may affect social and sexual interactions among group members....
    • Koala bellows and their association with the spatial dynamics of free-ranging koalas

      Ellis, William A.; Bercovitch, Fred B.; FitzGibbon, S.; Roe, P.; Wimmer, J.; Melzer, A.; Wilson, R. (2011)
      Acoustic communication mediates sociality in a variety of animals. One of the more ubiquitous vocal signals to have evolved is the sexual advertisement call of males. Koala (Phascolarctos cinereus) males emit a sonorous bellow call during the breeding season, but no detailed studies of the calling context appear to have been published. We used a novel remote sound detection network to monitor koala bellowing while simultaneously collecting koala behavioral data using collar-mounted GPS units. Our approach enabled us to examine fine scale temporal variation in vocalization and spatial movements of free-ranging koalas without direct behavioral observations. Bellow occurrence was susceptible to weather conditions, with fewer calls occurring when wind speed and temperatures were high. The number of bellow vocalizations recorded during an annual period mirrored breeding activity, with nearly all male bellows recorded during peak mating season. The distance traveled by koalas and the occurrence of koala bellows both peaked around midnight, but only female travel distance during the breeding season was temporally correlated with bellow occurrence. We conclude that environmental factors might trigger male bellowing to launch the breeding season and that these male vocal signals function more to attract females than to repel males. Female mate selection is probably an important component of male reproductive success in koalas, which is partly mediated by male bellow characteristics.
    • Mating strategies

      Steyaert, Sam M.J.G.; Zedrosser, Andreas; Swaisgood, Ronald R.; Filipczykova, Eva; Crudge, Brian; Dutta, Trishna; Sharma, Sandeep; Ratnayeke, Shyamala; Koike, Shinsuke; Leclerc, Martin; et al. (Cambridge University PressCambridge, 2020)
      The mating system and mating strategies of a species refer to the behavioral strategies used to obtain reproductive partners and ensure reproductive success. Common determining factors of mating systems and strategies are: the manner of mate acquisition, the number of mates obtained by an individual, as well as the absence or presence and duration of parental care….
    • Sound transmission in a bamboo forest and its implications for information transfer in giant panda ( Ailuropoda melanoleuca ) bleats

      Charlton, Benjamin D.; Owen, Megan A.; Keating, Jennifer L.; Martin-Wintle, Meghan S.; Zhang, Hemin; Swaisgood, Ronald R. (2018)
      Although mammal vocalisations signal attributes about the caller that are important in a range of contexts, relatively few studies have investigated the transmission of specific types of information encoded in mammal calls. In this study we broadcast and re-recorded giant panda bleats in a bamboo plantation, to assess the stability of individuality and sex differences in these calls over distance, and determine how the acoustic structure of giant panda bleats degrades in this species’ typical environment. Our results indicate that vocal recognition of the caller’s identity and sex is not likely to be possible when the distance between the vocaliser and receiver exceeds 20 m and 10 m, respectively. Further analysis revealed that the F0 contour of bleats was subject to high structural degradation as it propagated through the bamboo canopy, making the measurement of mean F0 and F0 modulation characteristics highly unreliable at distances exceeding 10 m. The most stable acoustic features of bleats in the bamboo forest environment (lowest % variation) were the upper formants and overall formant spacing. The analysis of amplitude attenuation revealed that the fifth and sixth formant are more prone to decay than the other frequency components of bleats, however, the fifth formant still remained the most prominent and persistent frequency component over distance. Paired with previous studies, these results show that giant panda bleats have the potential to signal the caller’s identity at distances of up to 20 m and reliably transmit sex differences up to 10 m from the caller, and suggest that information encoded by F0 modulation in bleats could only be functionally relevant during close-range interactions in this species’ natural environment.
    • The role of bioacoustic signals in koala sexual selection: Insights from seasonal patterns of associations revealed with GPS-proximity units

      Ellis, William A.; FitzGibbon, Sean; Pye, Geoffrey W.; Whipple, Bill; Barth, Ben; Johnston, Stephen; Seddon, Jenny; Melzer, Alistair; Higgins, Damien; Bercovitch, Fred B. (2015)
      Despite being a charismatic and well-known species, the social system of the koala (Phascolarctos cinereus—the only extant member of the family Phascolarctidae) is poorly known and much of the koala’s sociality and mating behaviors remain un-quantified. We evaluated these using proximity logging-GPS enabled tracking collars on wild koalas and discuss their implications for the mating system of this species. The frequency and duration of male-female encounters increased during the breeding season, with male-male encounters quite uncommon, suggesting little direct mating competition. By comparison, female-female interactions were very common across both seasons. Body mass of males was not correlated with their interactions with females during the breeding season, although male size is associated with a variety of acoustic parameters indicating individuality. We hypothesise that vocal advertising reduces the likelihood of male-male encounters in the breeding season while increasing the rate of male-female encounters. We suggest that male mating-season bellows function to reduce physical confrontations with other males allowing them to space themselves apart, while, at the same time, attracting females. We conclude that indirect male-male competition, female mate choice, and possibly female competition, mediate sexual selection in koalas.