Lower-level predictors and behavioral correlates of maximal aerobic capacity and sprint speed among individual lizards

The standard paradigm of organismal biology views lower-level traits (e.g. aspects of physiology) as determining organismal performance ability (e.g. maximal sprint speed), which in turn constrains behavior (e.g. social interactions). However, few studies have simultaneously examined all three levels of organization. We used focal observations to record movement behaviors and push-up displays in the field for adult male Sceloporus occidentalis lizards during the breeding season. We then captured animals, measured aspects of their physiology, morphology and performance, and counted ectoparasites and endoparasites as potential predictors of sprint speed and maximal oxygen consumption (V̇O2,max). Field behaviors were statistically repeatable, but not strongly so. Sprint speed and V̇O2,max were repeatable using residuals from regressions on body mass (speed: r=0.70; V̇O2,max: r=0.88). Both calf [standardized partial regression (path) coefficient B=0.53] and thigh [B=-0.37] muscle mass (as residuals from regressions on body mass) were significant predictors of sprint speed; hemoglobin concentration (B=0.42) was a predictor of V̇O2,max. In turn, V̇O2,max predicted the maximum number of four-legged push-ups per bout (B=0.39). In path analysis, log likelihood ratio tests indicated no direct paths from lower-level traits to behavior, supporting the idea that morphology, in the broad sense, only affects behavior indirectly through measures of performance. Our results show that inter-individual variation in field behaviors can be related to performance ability, which in turn reflect differences in morphology and physiology, although not parasite load. Given the low repeatability of field behaviors, some of the relationships between behavior and performance may be stronger than suggested by our results.

Reasons for unfulfilled breeding and transfer recommendations in zoos and aquariums

One of the primary tools for cooperatively managing animal populations within the Association of Zoos and Aquariums is through Breeding and Transfer Plan (BTP) recommendations. These recommendations consider population demographics, genetics, husbandry, and institutional needs and aim to improve population viability and long‐term sustainability. However, fulfilling (i.e., completing) recommendations can be complicated by biological and logistical challenges. We examined institutional reasons for unfulfilled Breed With, Do Not Breed, Hold, and Send To recommendations collected in surveys in PMCTrack, software for tracking recommendation fulfillment, using descriptive and text‐mining methods. Overall, 73 Animal Programs used PMCTrack to distribute 2335 surveys and accrued responses from 167 zoos and aquariums from 2007 to 2019, with a response rate of 56% (n = 1307). For Breed With recommendations, common reasons were related to an individual animal's status and a pair's breeding behavior; for all other recommendation types, reasons were often management or logistical factors. Most Breed With recommendations were attempted (≥55%) but did not result in detectable pregnancy/eggs or offspring, due to pair incompatibility or not enough time to successfully produce offspring. Hold and Do Not Breed recommendations were often unfulfilled because the BTP recommendation was replaced with an interim (i.e., updated) recommendation during the inter‐planning period. Our results support the importance of some common population management practices, such as maintaining breeding pairs/groups for multiple BTPs to improve mate familiarity, examining husbandry mechanisms to promote breeding success, and making a concerted effort to adhere to planning timelines to facilitate transfers in alignment with breeding seasons.

Institutional surveys revealed that unfulfilled breeding recommendations were mostly attempted but failed due to biological reasons

Send To, Hold, and Do Not Breed recommendations were typically unfulfilled due to management and logistical factors.

Prenatal exposure to low doses of atrazine affects mating behaviors in male guppies

Performing appropriate mating behaviors is crucial to male reproductive success, especially in species where mating is predominantly via female mate choice. Mating behaviors are hormonally regulated and may be sexually selected traits: courtship displays are selected via mate choice, while forced copulations and aggressive behaviors are selected for via intrasexual competition. Endocrine disrupting compounds interfere with proper hormonal functioning in exposed animals. Exposures during developmentally crucial life stages can have irreversible effects lasting through adulthood. I tested the effects of prenatal exposure to environmentally relevant doses of a commonly used herbicide, atrazine (1 and 13.5μg/L) on mating behaviors in male guppies. Guppies were used as a model organism to test the effects of atrazine exposure on wildlife reproductive health. Adult female guppies were mated and exposed to the treatments throughout the gestation period, and offspring born to them were raised without further treatment. At adulthood, the males were tested for the effects of prenatal exposure on their mating behaviors such as courtship displays, gonopodium swings, forced copulatory attempts, and competitive and aggressive behaviors towards rivals who were not exposed to atrazine. I also tested female preference for treated males compared to control males. Atrazine-exposed males were less likely to perform the mating behaviors, and performed them less frequently, than control males. Atrazine exposure also made males less aggressive towards rivals. Females preferred untreated males over atrazine-treated males. In all cases, a non-monotonic pattern was seen, highlighting the significance of low-dose exposures.

Heightened aggression and winning contests increase corticosterone but decrease testosterone in male Australian water dragons

Water dragons (Intellegama [Physignathus] lesueurii) are large (to >1m) agamid lizards from eastern Australia. Males are fiercely combative; holding a territory requires incessant displays and aggression against other males. If a dominant male is absent, injured or fatigued, another male soon takes over his territory. Our sampling of blood from free-ranging adult males showed that baseline levels of both testosterone and corticosterone were not related to a male's social tactic (territorial versus non-territorial), or his frequency of advertisement display, aggression, or courtship behavior. Even when we elicited intense aggression by non-territorial males (by temporarily removing territory owners), testosterone did not increase with the higher levels of aggression that ensued. Indeed, testosterone levels decreased in males that won contests. In contrast, male corticosterone levels increased with the heightened aggression during unsettled conditions, and were higher in males that won contests. High chronic male-male competition in this dense population may favor high testosterone levels in all adult males to facilitate advertisement and patrol activities required for territory maintenance (by dominant animals), and to maintain readiness for territory take-overs (in non-territorial animals). Corticosterone levels increased in response to intense aggression during socially unstable conditions, and were higher in contest winners than losers. A positive correlation between the two hormones during socially unstable conditions suggests that the high stress of contests decreased androgen production. The persistent intense competition in this population appears to exact a high physiological cost, which together with our observation that males sometimes lose their territories to challengers may indicate cycling between these two tactics to manage long-term energetic costs.

Melanin-based colouration as a potential indicator of male quality in the lizard Zootoca vivipara (Squamata: Lacertidae)

In many animals, aspects of colouration are hypothesized to convey information on the body condition or quality of individuals. This idea has been tested primarily for the carotenoid-based component of body colouration. The significance of other pigments in this context has received far less attention. In the common lizard, Zootoca vivipara, the degree of black patterning on the ventrum and throats is sexually dimorphic and varies considerably among individuals. In this study, we examine whether this melanin-based component of body colouration may reflect individual differences in quality (SVL, condition, immune response). We find that males (but not females) with a higher degree of ventral patterning mount a stronger phytohemagglutinin-induced immune response. The amount of black patterning does not correlate with body size, body condition, aspects of dorsal colouration or parasite load. We conclude that in male Zootoca vivipara, melanin-based ventral colouration may signal an aspect of immune capacity to sexual rivals or potential partners.

Activity predicts male reproductive success in a polygynous lizard

Activity patterns and social interactions play a key role in determining reproductive success, although this is poorly understood for species that lack overt social behaviour. We used genetic paternity analysis to quantify both multiple paternity and the relative roles of activity and social behaviour in determining reproductive success in a nondescript Australian lizard. During the breeding season we intensively followed and recorded the behaviour of a group of seven males and 13 females in a naturalistic outdoor enclosure to examine the relative roles of body size, activity and social interactions in determining male fertilization success. We found multiple paternity in 42% of clutches. No single behaviour was a significant predictor of male fertilization success in isolation, but male-female association, interactions and courtship explained 41% of the variation in male fertilization success. Males with the highest number of offspring sired invested heavily in interacting with females but spent very little time in interactions with males. These same males also sired offspring from more clutches. When taken collectively, an index of overall male activity, including locomotion and all social interactions, significantly explained 81% of the variation in the total number of offspring sired and 90% of the variation in the number of clutches in which males sired offspring. We suggest that the most successful male strategy is a form of endurance rivalry in which active mate searching and interactions with females have the greatest fitness benefits.