Designing anti-predator training to maximize learning and efficacy assessments

Despite the growing need to use conservation breeding and translocations in species’ recovery, many attempts to reintroduce animals to the wild fail due to predation post-release. Released animals often lack appropriate behaviours for survival, including anti-predator responses. Anti-predator training—a method for encouraging animals to exhibit wariness and defensive responses to predators—has been used to help address this challenge with varying degrees of success. The efficacy of anti-predator training hinges on animals learning to recognize and respond to predators, but learning is rarely assessed, or interventions miss key experimental controls to document learning. An accurate measure of learning serves as a diagnostic tool for improving training if it otherwise fails to reduce predation. Here we present an experimental framework for designing anti-predator training that incorporates suitable controls to infer predator-specific learning and illustrate their use with the critically endangered Hawaiian crow, ‘alalā (Corvus hawaiiensis). We conducted anti-predator training within a conservation breeding facility to increase anti-predator behaviour towards a natural predator, the Hawaiian hawk, ‘io (Buteo solitaries). In addition to running live-predator training trials, we included two control groups, aimed at determining if responses could otherwise be due to accumulated stress and agitation, or to generalized increases in fear of movement. We found that without these control groups we may have wrongly concluded that predator-specific learning occurred. Additionally, despite generations in human care that can erode anti-predator responses, ‘alalā showed unexpectedly high levels of predatory wariness during baseline assessments. We discuss the implications of a learning-focused approach to training for managing endangered species that require improved behavioural competence for dealing with predatory threats, and the importance of understanding learning mechanisms in diagnosing behavioural problems.

Predator-induced maternal effects determine adaptive antipredator behaviors via egg composition

In high-risk environments with frequent predator encounters, efficient antipredator behavior is key to survival. Parental effects are a powerful mechanism to prepare offspring for coping with such environments, yet clear evidence for adaptive parental effects on offspring antipredator behaviors is missing. Rapid escape reflexes, or “C-start reflexes,” are a key adaptation in fish and amphibians to escape predator strikes. We hypothesized that mothers living in high-risk environments might induce faster C-start reflexes in offspring by modifying egg composition. Here, we show that offspring of the cichlid fish Neolamprologus pulcher developed faster C-start reflexes and were more risk averse if their parents had been exposed to cues of their most dangerous natural predator during egg production. This effect was mediated by differences in egg composition. Eggs of predator-exposed mothers were heavier with higher net protein content, and the resulting offspring were heavier and had lower igf-1 gene expression than control offspring shortly after hatching. Thus, changes in egg composition can relay multiple putative pathways by which mothers can influence adaptive antipredator behaviors such as faster escape reflexes.

Vigilance Response of a Key Prey Species to Anthropogenic and Natural Threats in Detroit

Rapid urbanization coupled with increased human activity induces pressures that affect predator-prey relations through a suite of behavioral mechanisms, including alteration of avoidance and coexistence dynamics. Synergisms of natural and anthropogenic threats existing within urban environments exacerbate the necessity for species to differentially modify behavior to each risk. Here, we explore the behavioral response of a key prey species, cottontail rabbits (Sylvilagus floridanus), to pressures from humans, domestic dogs, and a natural predator, coyotes (Canis latrans) in a human-dominated landscape. We conducted the first camera survey in urban parks throughout Detroit, Michigan in 2017–2020 to assess vigilance response corresponding to a heterogeneous landscape created from variation in the occupancy of threats. We predicted a scaled response where cottontail rabbits would be most vigilant in areas with high coyote activity, moderately vigilant in areas with high domestic dog activity, and the least vigilant in areas of high human activity. From 8,165 independent cottontail rabbit detections in Detroit across 11,616 trap nights, one-third were classified as vigilant. We found vigilance behavior increased with coyote occupancy and in locations with significantly high domestic dog activity, but found no significant impact of human occupancy or their spatial hotspots. We also found little spatial overlap between rabbits and threats, suggesting rabbits invest more in spatial avoidance; thus, less effort is required for vigilance. Our results elucidate strategies of a prey species coping with various risks to advance our understanding of the adaptability of wildlife in urban environments. In order to promote coexistence between people and wildlife in urban greenspaces, we must understand and anticipate the ecological implications of human-induced behavioral modifications.

Urban fox squirrels exhibit habituation to humans but respond to stimuli from natural predators

Animals in urban areas that experience frequent exposure to humans often behave differently than those in less urban areas, such as less vigilance or anti-predator behavior. These behavioral shifts may be an adaptive response to urbanization and caused by habituation to humans. A possible negative consequence is cross-habituation to natural predators where urban animals exhibit reduced anti-predator behavior in the presence of humans but also to their natural predators. We tested the hypothesis that habituation to humans in urban populations of fox squirrels (Sciurus niger) causes cross-habituation to stimuli from two possible predators (hawks and domestic dogs). We exposed squirrels in multiple urban and less urban sites to acoustic playbacks of a control stimulus (non-predatory bird calls), a natural predator (hawk), and dogs and recorded their vigilance and three different anti-predator behaviors when a human approached them while either broadcasting one of these three playbacks or no playbacks at all. In trials with no playbacks, urban squirrels exhibited reduced vigilance and anti-predator behavior compared to those in less urban areas but there was little evidence that urbanization altered the correlations among the different behaviors we quantified. Urban squirrels exhibited increased vigilance and anti-predator behavior when exposed to a human paired with hawk playbacks compared to the control playbacks. This indicates that urban squirrels did perceive and assess risk to the natural predator appropriately despite exhibiting habituation to humans. There is currently little evidence that habituation to humans causes animals to lose their fear of natural predators.

Toxorhynchites Species: A Review of Current Knowledge

The increasing global incidence of mosquito-borne infections is driving a need for effective control methods. Vector populations have expanded their geographical ranges, while increasing resistance to chemical insecticides and a lack of effective treatments or vaccines has meant that the development of vector control methods is essential in the fight against mosquito-transmitted diseases. This review will focus on Toxorhynchites, a non-hematophagous mosquito genus which is a natural predator of vector species and may be exploited as a biological control agent. Their effectiveness in this role has been strongly debated for many years and early trials have been marred by misinformation and incomplete descriptions. Here, we draw together current knowledge of the general biology of Toxorhynchites and discuss how this updated information will benefit their role in an integrated vector management program.

The use of crotalaria as possible indirect agent to control Aedes aegypti L. (Diptera: Culicidae)

Aedes aegypti L. (Diptera: Culicidae) is a vector of arboviruses associated with dengue, chikungunya, zika and yellow fever. Based on empirical knowledge, plants belonging to genus Crotalaria (Fabaceae) attract dragonflies, which are the main natural predator to A. aegypti and help controlling populations of this mosquito. The aim of the present study is to investigate (i) whether Crotalaria is a food source for A. aegypti and (ii) whether Crotalaria attracts predators to this mosquito, mainly dragonflies. The study was carried out from January to March 2018 in two Crotalaria spectabilis Roth (Fabaceae) cultivation fields, which covered 100 m2 (each) in Missal County, Paraná State, Brazil. Samples of all arthropods foraging on C. spectabilis were collected. Observations in situ were carried out to investigate whether A. aegypti individuals visit C. spectabilis flowers. In total, 14,967 arthropods were recorded foraging on C. spectabilis (288 in cultivation field 1 and 14,679 in cultivation field 2). Dragonflies and damselflies were recorded foraging on C. spectabilis crops, but no A. aegypti individual was recorded in active collections and observations in situ. These results indicate that C. spectabilis works as food source and/or place used by several arthropods to find preys. The incidence of dragonflies and damselflies flying in C. spectabilis monocultures indicates that these plants attract dragonflies, as well as that Crotalaria can help indirectly controlling A. aegypti populations.