Biomedical subjects

Fabien Aubret

Publications and source records attributed to Fabien Aubret.

4 recordsLinked to original sources

PubMed2005

Influence of body reserves and eye opacity on foraging behaviours of tiger snakes.

Physiological states such as reproductive stage, parasite load, body condition, and environmental conditions, influence behaviours in complex ways. According to the Clark's asset-protection principle (Clark, 1994. Behav Ecol 5:159-170), individuals in good body condition take fewer predation risks than conspecifics in lesser condition. In many ectotherms, foraging, digestion, and moulting require an elevation of the metabolism achieved through intensive basking, thereby increasing the risk of being detected by predators. Using four experimental groups of snakes, we showed that two independent physiological states, (1) the presence of prey in the stomach and (2) eye opacity associated with moulting, increase predator vulnerability. In a parallel experiment, two groups of snakes were maintained on contrasting diets (high food intake vs. low food intake) for 6 months. Apart from sloughing periods, most individuals (89%) accepted their meal irrespective of food treatment. Consequently, well-fed snakes exhibited higher body condition (one third physiological state) relative to less-fed individuals. During sloughing events, however, well-fed individuals often refused (78%) to eat while the less-fed individuals readily accepted (86%) their meal despite eye opacity. Individuals with less body reserves accepted the cumulative risks owing to eye opacity and stomach fullness. By contrast, well-fed snakes remained more "prudent" (i.e., exhibited behaviours that depended on their internal state). Our results show that snakes can adjust their foraging "decision" by combining different physiological informations.

Analysis of Variance↗

PubMed2005

Tail loss, body condition and swimming performances in tiger snakes, Notechis ater occidentalis.

In limbless tetrapods such as snakes, propulsive forces are generated by lateral undulations of the body and of the tail. In a large population of tiger snakes from Western Australia, tail loss was extremely common (58% of the individuals) and often very severe (more than two-thirds of the tail was missing in 14% of the cases, and in some instances, the tail was totally lost). Tail loss was not however correlated with body size, mass or body condition of wild individuals, and hence did not influence their abilities to acquire resources. These large venomous snakes exhibit marked aquatic habits. Locomotor tests in controlled conditions revealed that tail loss had a significant negative influence on burst swimming performances. However, no effect was found on routine swimming speed and total distance travelled over 5 min. These results suggest that a long and slender tail, although important for maximal speed, is not necessarily relevant for the locomotor abilities required for successful hunting. Tail-damaged individuals outnumbered intact snakes, suggesting that tail loss did not severely compromise survival. Overall, in this species, a slight deterioration of maximal speed due to severe tail loss probably has a low (undetectable) ecological impact, at least for adults.

Animals↗

PubMed2004

Evolutionary biology: adaptive developmental plasticity in snakes.

The morphology of organisms is generally well matched to their environment, presumably because expression of their genes is tailored either at the population or the individual level to suit local conditions: for example, snake populations that persistently encounter large prey may accumulate gene mutations that specify a large head size, or head growth may be increased in individual snakes to meet local demands (adaptive developmental plasticity). Here we test the relative contributions of genetics and environment to the jaw sizes of two tiger snake populations: one that consumes small prey on the mainland, and an island population that relies on larger prey and has a larger jaw size. Although the idea of adaptive plasticity in response to environmental pressures is controversial, we find that both factors influence the difference in jaw size between the two populations, and the influence of developmental plasticity is greater in the island population.

Adaptation, Physiological↗

PubMed2002

Fat is sexy for females but not males: the influence of body reserves on reproduction in snakes (Vipera aspis).

Reproduction is energetically expensive for both sexes, but the magnitude of expenditure and its relationship to reproductive success differ fundamentally between males and females. Males allocate relatively little to gamete production and, thus, can reproduce successfully with only minor energy investment. In contrast, females of many species experience high fecundity-independent costs of reproduction (such as migration to nesting sites), so they need to amass substantial energy reserves before initiating reproductive activity. Thus, we expect that the relationship between energy reserves and the intensity of reproductive behavior involves a threshold effect in females, but a gradual (or no) effect in males. We tested this prediction using captive vipers (Vipera aspis), dividing both males and females into groups of high versus low body condition. Snakes from each group were placed together and observed for reproductive behavior; sex-steroid levels were also measured. As predicted, females in below-average body condition had very low estradiol levels and did not show sexual receptivity, whereas males of all body condition indices had significant testosterone levels and displayed active courtship. Testosterone levels and courtship intensity increased gradually (i.e., no step function) with body condition in males, but high estradiol levels and sexual receptivity were seen only in females with body reserves above a critical threshold.

Adipose Tissue↗