Bob B. M. Wong

Habitat structure mediates thermoregulation, foraging opportunities, and access to refugia, shaping how animals use space and encounter risk. Dune–swale mosaics provide sharp structural contrasts over short distances, offering a natural test of structure–assemblage links and spacing relative to shelter. We compared lizard assemblages and the positions of active lizards relative to vegetative cover across interdunal swales and adjacent sand dunes in central South Australia. At replicated sites in Arid Recovery Reserve and Andamooka Pastoral Station, we quantified vegetation and ground‐layer structure, sampled assemblages with pitfall traps and active searches, and measured each active lizard's distance to the nearest vegetative refuge. We tested whether the expected structural contrast between dunes and swales was evident at our study sites, whether lizard community composition and assemblage metrics differed between landforms, and whether active lizards in structurally simpler habitat occurred closer to vegetative cover than those in more complex habitat. Dunes were more structurally complex than swales, lizard communities differed significantly between landforms, and abundance was higher on dunes, whereas richness and diversity were broadly comparable. However, active lizards in both landforms occurred at similar distances to vegetative cover. These findings identify habitat structure as a key driver of assemblage differences, while showing that we did not detect a significant habitat‐level difference in active lizards' distance to vegetative cover under the present sampling design. We interpret implications for predation risk broadly in a multi‐predator context and recommend coupling behavioural metrics with predator‐activity indices and repeating sampling across wet and dry years.

Sexual selection is a potent evolutionary force shaping both precopulatory courtship behavior and postcopulatory sperm traits, with male reproductive effort often adjusted to social and mating context. Endocrine-disrupting contaminants are predicted to alter how males allocate reproductive effort, yet their behavioral effects across different mating contexts remain poorly understood. We examined whether exposure to 17α-ethinylestradiol (EE2; 43 to 1,100 ng/L), a synthetic estrogen used in the contraceptive pill that enters aquatic systems via wastewater effluent, alters male courtship behavior and sperm traits in a freshwater fish (Dermogenys collettei). Using assays in which males encountered females either sequentially or simultaneously, we quantified courtship behavior and latency to interact, alongside sperm viability, morphology, and performance. Exposure to high EE2 consistently reduced male mating effort. Exposed males were slower to initiate interactions with females and expressed less courtship behavior in both sequential and simultaneous assays. In contrast, EE2 had no detectable effects on sperm traits, and male preferences for female gravid spot size were unaffected. These findings suggest estrogenic pollution can disproportionately reduce mating effort, revealing a decoupling between behavioral and postcopulatory responses.

Pharmaceutical pollution is a global environmental threat, with antidepressants contributing a substantial proportion of pharmaceutical contaminant detections worldwide. The antidepressant fluoxetine is commonly detected in aquatic environments and has been reported to impact ecologically important behavioral and physiological traits in exposed wildlife. However, relatively few studies have examined possible effects of fluoxetine on both behavior and metabolic rate, particularly over ecologically relevant exposure timescales. Accordingly, we investigated the impacts of long-term fluoxetine exposure on foraging and antipredator behavior, metabolic rate, and morphology in female guppies (Poecilia reticulata). Fish were exposed to 1 of 3 treatments—an unexposed control (0 ng L−1), or low or high fluoxetine (mean measured concentrations: 30 ng L−1 and 292 ng L−1, respectively)—for 8 mo in a semi-natural mesocosm system, corresponding to ∼2 to 3 overlapping generations. Following exposure, we quantified foraging and antipredator behavior in the presence or absence of a live predator, the spangled perch (Leiopotherapon unicolor). We then measured the rate of oxygen consumption (V˙O2) of the guppies as a proxy for standard metabolic rate, and recorded mass, standard length, and body condition as morphological measurements. Our results show that long-term fluoxetine exposure did not significantly affect the behavior, metabolic rate, or morphology of female guppies. Considered alongside previous work, our findings emphasize the importance of exposure duration in mediating the impacts of fluoxetine on fitness-related traits, with continued research being essential in identifying potential mechanisms that underpin these findings.

The executive functions are a suite of cognitive-control processes that enable goal-directed behaviour. Executive functioning is vital in allowing animals to adapt their behaviour to changing environmental conditions, which is a key determinant of the success of individuals, populations, and species under anthropogenic change. Despite this, very little is known about the mechanisms that underpin executive functioning in animals and how it manifests in behaviour. Moreover, whether and how executive functioning is impacted by environmentally realistic levels of chemical pollution is completely unknown, despite neuroactive pollutants, such as pharmaceuticals, having become widespread in ecosystems around the globe. We employed the Free Movement Pattern Y-maze to investigate how executive functioning manifests in decision-making and behaviour in a wild population of guppies ( Poecilia reticulata ), and whether this was disrupted by exposure to two environmentally realistic concentrations (9 ng/L or 309 ng/L) of the neuroactive pharmaceutical pollutant amitriptyline. We found that two of the three domains of executive function—working memory and cognitive flexibility—actively regulated cognition to inform behaviour during maze exploration. However, the role of executive functioning in directing navigation behaviour was not affected by exposure to amitriptyline. Given that neuroactive pharmaceuticals are increasingly detected in waterways, and executive functioning is critical for behaviours that dictate fitness, it is crucial that we better understand whether and how these contaminants affect executive functioning, and what implications this may have for wildlife living in human-impacted ecosystems.

Psychoactive pharmaceuticals have been increasingly detected across the environment worldwide. Alarmingly, these pollutants disrupt ecologically important behaviours in exposed wildlife, both at the population-level and individual-level. Individual-level responses, such as the differences between individuals (i.e. behavioural individuality), are a key facilitator of population resilience and adaptive potential. Nevertheless, the effects of pharmaceutical exposure on behavioural individuality across social contexts are currently poorly understood. To address this, we investigated whether a 21-day exposure to an environmentally realistic level (1 µg l−1) of a ubiquitous pollutant, the antidepressant venlafaxine, caused population- and individual-level behavioural responses in juvenile southern pygmy perch (Nannoperca australis), when tested individually and in the presence of a conspecific. We found that, in the presence of another fish, exposed individuals were less exploratory than controls, but this effect was not observed while in social isolation. Moreover, exposed fish differed less from each other (i.e. lower behavioural individuality) in their activity in the individual trials and their exploration in the paired trials. Lastly, venlafaxine also reduced body condition in exposed fish. Our findings suggest that psychoactive pharmaceuticals can alter body condition and behaviour across ecologically relevant contexts, with potential implications for the adaptive capacity and population resilience of exposed wildlife.

In brief: Pharmaceutical pollution can have serious consequences for wildlife reproduction. This paper reveals that exposure to the pervasive oestrogenic pollutant 17ɑ-ethinylestradiol does not impact female reproduction in a nonmodel viviparous fish. Pharmaceuticals are fast becoming a major source of environmental pollution. Many pharmaceuticals are endocrine disruptors and can thus interfere with the endocrine system of exposed organisms, leading to a suite of behavioural and physiological alterations. While numerous studies have shown that exposure to pharmaceutical contaminants can disrupt the reproductive ecology of oviparous fishes, far less attention has been given to understanding the impacts on viviparous fishes, despite their ecological and evolutionary importance. Here, we investigated the impacts of the pharmaceutical contaminant 17ɑ-ethinylestradiol (EE2) on the reproductive biology of a marine livebearer, the Southern crested weedfish (Cristiceps australis). Adult weedfish were exposed to one of three nominal concentrations of EE2 (0, 30, and 300 ng/L) for 14 days. We then assessed the impacts of exposure on morphology of both sexes, and female gametogenesis. In doing so, we found no differences in the body length, weight, or condition of fish between treatment groups. We additionally found no differences in gonadosomatic index or gametogenesis between exposed and unexposed females. In contrast to reports in other taxa, our findings suggest that short-term exposure to EE2 does not produce detectable effects on weedfish growth and reproduction. However, the extent to which exposure duration influences these responses is unknown. Ultimately, these results emphasize the importance of assessing the effects of EE2 on a diverse range of organisms if we are to gain a more comprehensive understanding of its ecological impacts.