Exploratory and defensive behaviours change with sex and body size in eastern garter snakes (Thamnophis sirtalis)

Spatial ecology to strengthen invasive snake management on islands

Knowledge on the spatial ecology of invasive predators positively contributes to optimizing their management, especially when involving cryptic and secretive species, such as snakes. However, this information is lacking for most invasive snakes, particularly on islands, where they are known to cause severe ecological and socio-economic impacts. This research is focused on assessing the spatial ecology of the California kingsnake (Lampropeltis californiae) on Gran Canaria to strengthen management actions. We monitored 15 radio-tagged individuals once per day on 9-11 days per month from July 2020 to June 2021 to calculate the species' home range and describe annual activity patterns in the invaded range. To account for the species' diel activity during the emergence period, we additionally monitored snakes from January to May 2021 during three consecutive days per month in four different time intervals each day. We detected movement (consecutive detections at least 6 m apart) in 31.68% of the 1146 detections during the whole monitoring period. Movements most frequently detected were shorter than 100 m (82.24%), and among them the range 0-20 m was the most recurrent (27.03%). The mean distance of movement was 62.57 ± 62.62 m in 1-2 days. Average home range was 4.27 ± 5.35 ha-calculated with the Autocorrelated Kernel Density Estimator (AKDE) at 95%-and did not significantly vary with SVL nor sex. We detected an extremely low value of motion variance (0.76 ± 2.62 σ²m) compared to other studies, with a general inactivity period from November to February, January being the less active month of the year. Diel activity was higher during central and evening hours than during early morning and night. Our results should be useful to improve control programs for this invasive snake (e.g., trap placement and visual survey guidance) on Gran Canaria. Our research highlights the importance of gathering spatial information on invasive snakes to enhance control actions, which can contribute to the management of secretive invasive snakes worldwide.

Extrinsic traits consistently drive microhabitat decisions of an arboreal snake, independently of sex and personality

One pivotal topic on habitat selection is to understand the influence of intrinsic and extrinsic factors on the selection process. Although the effect of some extrinsic variables and sex has been extensively studied, almost nothing is known about the effect of personality, particularly on snakes. Here we addressed the relative importance of extrinsic (tree-related) and intrinsic (sex and personality) factors driving microhabitat selection decisions of a nocturnal tree snake (Leptodeira annulata). We implemented a protocol to quantify the influence of personality and sex on the role of extrinsic variables on microhabitat selection. First, we conducted three behavioral experiments to extract the shyness-boldness and avoidance-exploitation personality traits of male snakes. Then, we evaluated the role of sex and personality on the effect of tree-traits (thickness, canopy cover and shelter availability) on microhabitat selection, using two-step conditional logistic regression. Snakes consistently selected tree trunks, preferably thick and with high canopy cover and shelter availability, independently of their sex of personality. For this species, only extrinsic variables determined microhabitat decisions. Our protocol will aid to quantify the role of personality on microhabitat selection of other species and understand whether this is an important variable in habitat decision-making or not.

Capture vulnerability of sea turtles on recreational fishing piers

Capture vulnerability of commercial and recreational fishes has been associated with behavioral, morphological, and life-history traits; however, relationships with non-target species, such as sea turtles, have not been adequately studied. We examined species composition, timing of captures, morphological variables including body size and head width, and body condition of sea turtles captured from a recreational fishing pier in the northern Gulf of Mexico and of sea turtles captured in the waters adjacent to the pier. From 2014 to 2019, 148 net captures and 112 pier captures of three sea turtle species were documented. Green turtles were captured most frequently in the net and on the pier. Turtles captured from the pier were larger than those captured in the net. There was no difference in head width between net-caught and pier-caught turtles; however, small sample sizes limited those comparisons. The body condition index was lower for pier-caught than net-caught Kemp';s ridleys but did not differ with green turtles or loggerheads. Differences were also observed in the timing of capture on the pier as compared to in the net. Finally, the relationship between size, body condition, and pier-capture vulnerability suggests these are complex interactions. Mortality of sea turtles captured from fishing piers could be selecting against bolder individuals, which may result in changes in sea turtle population demographics over a long time period.

A meta-analysis of sex differences in animal personality: no evidence for the greater male variability hypothesis

The notion that men are more variable than women has become embedded into scientific thinking. For mental traits like personality, greater male variability has been partly attributed to biology, underpinned by claims that there is generally greater variation among males than females in non-human animals due to stronger sexual selection on males. However, evidence for greater male variability is limited to morphological traits, and there is little information regarding sex differences in personality-like behaviours for non-human animals. Here, we meta-analysed sex differences in means and variances for over 2100 effects (204 studies) from 220 species (covering five broad taxonomic groups) across five personality traits: boldness, aggression, activity, sociality and exploration. We also tested if sexual size dimorphism, a proxy for sex-specific sexual selection, explains variation in the magnitude of sex differences in personality. We found no significant differences in personality between the sexes. In addition, sexual size dimorphism did not explain variation in the magnitude of the observed sex differences in the mean or variance in personality for any taxonomic group. In sum, we find no evidence for widespread sex differences in variability in non-human animal personality.

Sex-specific growth is mirrored in feeding rate but not moulting frequency in a sexually dimorphic snake

Sexual size dimorphism (SSD), commonly observed in snakes, may arise from a different growth rate between the sexes. This indicates a sex-specific resource intake that is in fact observable in free-living snakes. It is not so well known whether the sexes can express differential feeding rates under conditions unconstrained by spatial accessibility, competition, etc. Here, I studied sex-specific variation in growth, its correlate-moulting frequency, and feeding rate in a captive group of sexually dimorphic banded water snakes (Nerodia fasciata) with access to food unconstrained by predation, competition or space. I showed that the sexes did indeed differ in relative mass growth in that females grew faster than males (p = 0.02), but such differences were not apparent in the moulting rate (p = 0.19). Such differential growth was mirrored in the sex-specific feeding rate, with females ingesting a larger number of meals than males (p = 0.004). Such variation in feeding rate may be governed by an individual's energy expenditure and can be interpreted as a behavioural tendency that contributes to SSD development, independently of other behavioural characteristics. Sex-specific resource demands may drive the differential effects of increasing resource scarcity on both sexes.

Test-dependent expression of behavioral syndromes: A study of aggressiveness, activity, and stress of chub

Aggressiveness has been one of the behavioral traits most examined with various standard testing methods. We used two distinct methods (the mirror and the real opponent tests) to evaluate individual aggression and relate it to the activity and individual stress of chub (Squalius cephalus L.). Three hypotheses were formulated and tested: (a) there is a significant positive relationship between the aggressiveness of individuals measured with the mirror and the real opponent tests, indicating their convergent validity; (b) the irregularities in response to the aggressiveness and activity tests lead to the context-specific expression of the behavioral syndromes; and (c) there is a significant positive relationship between the stress induced in individuals by both tests of aggressiveness, demonstrating individually consistent stress-coping strategies. The first and the second hypothesis were confirmed, while the third hypothesis was rejected. Our results suggest that particular tests of aggressiveness could act as a situation with high strength, leaving little variation between individual responses. Thus, we propose that for the proper interpretation of various studies using different tests to study identical behavioral traits, it is important to consider the convergent validity of not only the tested behavioral traits but also the individual stress responses. The chub also showed stress relieve through aggressiveness, suggesting the species as a prospective animal model to the study interaction between the stress and the aggressiveness. A detailed aggression ethogram of chub was provided to facilitate the use of this specie in future studies.

Covariations between personality behaviors and metabolic/performance traits in an Asian agamid lizard (Phrynocephalus vlangalii)

Ecological factors related to predation risks and foraging play major roles in determining which behavioral traits may mediate life history trade-offs and, therefore, the pace-of-life syndrome (POLS) structure among behavioral, physiological, and life-history traits. It has been proposed that activity/exploration or risk-taking behaviors are more likely to impact resource acquisition for organisms (individuals, populations, and species) foraging on clumped and ephemeral food sources than for organisms foraging on abundant and evenly distributed resources. In contrast, vigilance or freezing behavior would be expected to covary with the pace of life when organisms rely on food items requiring long bouts of handling. Nevertheless, it remains unclear how general this pattern is. We tested this hypothesis by examining the associations between exploration/risk-taking behaviors and metabolic/performance traits for the viviparous agamid lizard, Phrynocephalus vlangalii. This species forages on sparse and patchy food sources. The results showed positive correlations between exploration and endurance capacity, and between bite force and risk-taking willingness. Our current findings, in conjunction with our previous work showed no correlations between freezing behavior and performance in this species, support the idea that behaviors in life-history trade-offs are natural history-dependent in P. vlangalii, and provide evidence that behavioral types play functional roles in life history trade-offs to supporting POLS hypothesis.

Mary CM. Does the use of a multi-trait, multi-test approach to measure animal personality yield different behavioural syndrome results?

A multi-trait, multi-test approach to investigate the convergence or discrimination between behavioural tests putatively targeting the same or different animal personality traits has been recommended, yet whether and how the approaches affect the identification of behavioural syndrome(s), the suite of correlated personality traits, requires investigation. Here, we used behavioural measures collected from five commonly used behavioural tests targeting three personality traits, evaluated their convergence/discrimination through exploratory factor analysis (EFA), and then explored whether the identification of syndrome changed based on the approach we used to quantify personality traits. Our results indicated that tests presumably targeting the same personality trait actually measured distinct behavioural aspects. Syndrome defined using correlation changed due to how we identified personality traits, but not when using structural equation models (SEMs). Overall, this study emphasizes that it is critical to clarify the approach and terms we use for ‘personality traits’ in the field of animal personality.

Bigger babies are bolder: effects of body size on personality of hatchling snakes

An animal’s susceptibility to risk may be partly dependent on its body size. But are larger individuals bolder? We assessed this question by measuring time to emerge from a shelter in repeated trials on hatchling keelback snakes (Tropidonophis mairii). Estimates of repeatability of emergence times suggested they measure some underlying personality dimension related to boldness. Larger hatchlings emerged from shelter sooner than small ones. Hatchling mass of keelbacks is substantially influenced both by maternal phenotype and by incubation conditions. Given the environmental basis of much of the variation in offspring size, the size-boldness association may reflect a facultative ability to adjust behavioural tactics to body size, as well as innate differences in personality traits between large versus small hatchlings. The link between size and boldness suggests that the survival advantage of larger offspring size in this population may be driven by snake behaviour as well as morphology.