Male energy reserves, mate-searching activities, and reproductive success: alternative resource use strategies in a presumed capital breeder

Effects of environmental factors and intraspecific niche overlap on the body and ecological characteristics of red-tongued pit vipers (Gloydius ussuriensis)

The body condition of a snake species provides important physiological, morphological, and ecological information that elucidates its habits, life cycle, and competitive relationships. We measured the body size and condition of the wild Gloydius ussuriensis population in South Korea from 2018 to 2022, analyzed the degree of intraspecific niche overlap, and identified the geographic and climatic factors affecting their body condition. We found that the females were longer than the males. The body condition index (BCI) of G. ussuriensis differed depending on sex and season; the BCI of the females and males was highest in August and October, respectively. Environmental factors related to altitude and temperature affected the body condition of G. ussuriensis; BCI increased as the mean annual temperature and winter temperature increased; however, it increased when the annual temperature range decreased. The mean Pinaka index was 0.96, indicating a high degree of niche overlap; however, the niche overlap among the neonates was less than that among the adults and juveniles. To elucidate the causes of niche overlap and mechanisms behind the intraspecific competition among G. ussuriensis individuals, the habitat and utilization of food resources at different development stages of G. ussuriensis should be further investigated.

Spatial ecology, activity patterns, and habitat use by giant pythons (Simalia amethistina) in tropical Australia

Although giant snakes are abundant in some tropical forests, their ecology is far less well-known than for smaller species of snakes in cooler climates. Information on spatial ecology can clarify management issues such as the sizes and types of habitats needed for conservation. We radio-tracked 27 scrub pythons (Simalia amethistina; snout-vent lengths 2.02 to 3.70 m) in Cape York, near the northeastern tip of Australia, for a mean period of 426 days (up to 1001 days) per snake. Home ranges were larger in males than females (means 0.60 vs. 0.28 km²) and overlapped considerably among individuals. All snakes used rainforest habitat, but seasonal shifts into open woodland were common. Snakes were active primarily by night, with larger snakes hunting less of the time overall, and more often by day. Hunting behaviour was seen more often during the wet season than the dry season. Average daily displacement was < 10 m, typically involving a shift from diurnal refuge to nocturnal ambush-site. A reliance on sit-and-wait predation results in small home ranges and limited movements, despite the large body size of this species.

Phylogenetic analysis of macroecological patterns of home range area in snakes

A home range is the area animals use to carry out routine activities such as mating, foraging, and caring for young. Thus, the area of a home range is an important indicator of an animal's behavioural and energetic requirements. While several studies have identified the factors that influence home range area (HRA), none of them has investigated global patterns of HRA among and within snake species. Here, we used a phylogenetic mixed model to determine which factors influence HRA in 51 snake species. We analysed 200 HRA estimates to test the influence of body mass, sex, age, diet, precipitation, latitude, winter and summer temperature, while controlling for the duration of the study and sample size. We found that males had larger HRA than females, that adults had larger HRA than juveniles, and that snake species with fish-based diets had smaller HRA than snake species with terrestrial vertebrate-based and invertebrate-based diets. We also found that HRA tended to increase as mean winter temperature decreases and tended to decrease with precipitation. After accounting for these factors, the phylogenetic heritability of HRA in snakes was low (0.21 ± 0.14). Determining the factors that dictate macroecological patterns of space use has important management implications in an era of rapid climate change.