Emergent patterns between salamander prey and their predators

The relationships between toad behaviour, antipredator defences, and spatial and sexual variation in predation pressure

BACKGROUND

Animal behaviour is under strong selection. Selection on behaviour, however, might not act in isolation from other fitness-related traits. Since predators represent outstanding selective forces, animal behaviour could covary with antipredator defences, such that individuals better suited against predators could afford facing the costs of riskier behaviours. Moreover, not all individuals undergo equivalent degrees of predation pressure, which can vary across sexes or habitats. Individuals under lower predation pressure might also exhibit riskier behaviours.

METHODS

In this work, I tested these hypotheses on natterjack toads (Epidalea calamita). Specifically, I gauged activity time, exploratory behaviour and boldness in standard laboratory conditions, and assessed whether they correlated with body size and antipredator strategies, namely sprint speed, parotoid gland area and parotoid gland colour contrast. Additionally, I compared these traits between sexes and individuals from an agrosystem and pine grove, since there is evidence that males and agrosystem individuals are subjected to greater predation pressure.

RESULTS

Sprint speed as well as parotoid gland contrast and size appeared unrelated to the behavioural traits studied. In turn, body mass was negatively related to activity time, boldness and exploration. This trend is consistent with the fact that larger toads could be more detectable to their predators, which are mostly gape unconstrained and could easily consume them. As predicted, females exhibited riskier behaviours. Nonetheless, agrosystem toads did not differ from pine grove toads in the behavioural traits measured, despite being under stronger predation pressure.

SquamataBase: a natural history database and R package for comparative biology of snake feeding habits

Public databases in taxonomy, phylogenetics and geographic and fossil occurrence records are key research tools that provide raw materials, on which broad-scale analyses and synthesis in their respective fields are based. Comparable repositories for natural history observations are rare. Publicly available natural history data on traits like diet, habitat and reproduction are scattered across an extensive primary literature and remain relatively inaccessible to researchers interested in using these data for broad-scale analyses in macroecology and macroevolution. In this paper, I introduce SquamataBase, an open-source R package and database of predator-prey records involving the world’s snakes. SquamataBase facilitates the discovery of natural history observations for use in comparative analyses and synthesis and, in its current form, contains observations of at least 18,304 predator individuals comprising 1,227 snake species and at least 58,633 prey items comprising 3,231 prey taxa. To facilitate integration with comparative analysis workflows, the data are distributed inside an R package, which also provides basic functionality for common data manipulation and filtering operations. Moving forward, the continued development of public natural history databases and their integration with existing digitisation efforts in biodiversity science should become a priority.

Reciprocal Role of Salamanders in Aquatic Energy Flow Pathways

Many species of salamanders (newts and salamanders per se) have a pivotal role in energy flow pathways as they include individuals functioning as prey, competitors, and predators. Here, I synthesize historic and contemporary research on the reciprocal ecological role of salamanders as predators and prey in aquatic systems. Salamanders are a keystone in ecosystem functioning through a combination of top–down control, energy transfer, nutrient cycling processes, and carbon retention. The aquatic developmental stages of salamanders are able to feed on a wide variety of invertebrate prey captured close to the bottom as well as on small conspecifics (cannibalism) or other sympatric species, but can also consume terrestrial invertebrates on the water surface. This capacity to consume allochthonous resources (terrestrial invertebrates) highlights the key role of salamanders as couplers of terrestrial and aquatic ecosystems (i.e., aquatic–terrestrial linkages). Salamanders are also an important food resource for other vertebrates such as fish, snakes, and mammals, covering the energy demands of these species at higher trophic levels. This study emphasizes the ecological significance of salamanders in aquatic systems as central players in energy flow pathways, enabling energy mobility among trophic levels (i.e., vertical energy flow) and between freshwater and terrestrial habitats (i.e., lateral energy flow).