Ronald R. Swaisgood

Subsidized predators—present at higher densities due to anthropogenic activity—pose a significant conservation challenge to many at‐risk species and are often one of the main factors influencing the decline of many beach‐nesting birds. This study evaluates the efficacy of nest exclosures as an anti‐predator management intervention for western snowy plovers ( Anarhynchus nivosus nivosus ). We base our analyses on 8 years of intensive monitoring of two populations located on military bases in southern California. After placing nest exclosures on a subset of monitored nests, we surveyed all nesting areas at least twice weekly to document nest outcomes and, when possible, infer causes of nest loss. Our findings provide strong evidence supporting the use of exclosures in systems experiencing high predation pressure from subsidized predators. Without exclosures, nest predation rates reached approximately 27% across the nesting cycle, whereas nests protected by exclosures experienced predation rates of less than 2%, representing a ~16‐fold decrease. This intervention significantly improved nest survival, increasing the probability of hatching from 65% to 89% over a 32‐day nesting period. Additionally, we found no significant difference in nest abandonment rates between protected and unprotected nests, suggesting that exclosures did not contribute to increased adult mortality in this study system though it has been documented in other systems. Importantly, nest exclosures complemented, rather than replaced, predator control measures and habitat management strategies aimed at reducing predation risk. Furthermore, ecological factors, such as nest crypsis, were associated with reduced predation, reinforcing the importance of natural camouflage. Our findings underscore the effectiveness of exclosures in protecting nests and highlight the need for integrated conservation strategies that incorporate multiple protective measures to manage threats from subsidized predators.

Quantifying thermoregulatory parameters, such as preferred and realized body temperatures, is essential for predicting ectotherm responses to climate change, and accurate estimates of internal body temperature are central to these efforts. In reptiles, cloacal temperature serves as the primary field- and laboratory-standard proxy for internal body temperature. Infrared thermography (IRT) is increasingly used to estimate internal body temperatures of small ectotherms because it minimizes disturbance to animal behaviour, thereby improving data quality. Although IRT has advantages over traditional contact methods, it relies on correlations between external and internal body temperatures, which can vary across taxa. To evaluate IRT’s efficacy for estimating internal temperature of small turtles, we compared surface and cloacal temperatures of hatchling Mojave desert tortoises (Gopherus agassizii) under warming, elevated temperature and cooling conditions on two laboratory thermal gradients spanning moderate to extreme temperature ranges. Among five measured shell and body regions, shell temperatures correlated most strongly with cloacal temperatures. IRT produced accurate estimates during elevated temperature and cooling phases but was less accurate during warming from low initial body temperatures, particularly under steeper thermal gradients. We also evaluated IRT in two additional contexts: hatchling rearing enclosures and a behavioural experiment. Shell and cloacal temperatures aligned closely in rearing enclosures but exhibited larger discrepancies in the behavioural experiment. Our findings suggest that IRT is a promising tool for non-invasive estimation of cloacal temperature in hatchling desert tortoises (25–101 g). This tool is most useful under moderate thermal conditions when body temperatures are near thermal equilibrium but should be used with caution during periods of rapid temperature change when surface and internal temperatures may diverge. Once validated within a given study system, IRT can provide a practical alternative to traditional methods for monitoring body temperature while reducing disturbance and handling stress that may alter natural thermal behaviour.

Conservation breeding programs (CBPs) can play a vital role in preventing extinction. Housing considerations are particularly important in CBPs because suboptimal enclosures can negate efforts to promote animal well‐being, survival, reproduction, and the retention of natural behaviors. Moreover, the quality and quantity of enclosures also influence the social environment experienced by animals, an important determinant of reproduction. Extinct in the wild, the territorial ‘Alalā (Hawaiian crow, Corvus hawaiiensis ) is the subject of intensive conservation breeding at two purpose‐built facilities in Hawai'i. To examine the role of space and social environment in this CBP, we evaluated reproductive outcomes for ‘Alalā pairs held in different‐sized enclosures (i.e., housed in one vs. two chambers within a stand‐alone aviary building), corresponding to important differences in social context, including the amount of space and enclosure architecture available for the pair, which we label “social crowding.” We tested the hypothesis that social crowding adversely impacts nest quality, clutches laid, egg fertilization, and hatching success. We found social crowding negatively impacted nest quality and decreased the probability of clutch production, suggesting that stress, derived from being housed in a social arrangement that does not align with the territorial nature of ‘Alalā, may compromise reproductive behavior and/or physiology. We did not find statistical evidence that crowding affected egg fertilization or hatching success, thus the impacts of crowding appear to manifest during the earlier reproductive stages. Broadly, our findings underscore the importance of aviary design and social context in avian CBPs and raise concerns about reduced breeding output due to housing territorial birds in smaller enclosures with denser social arrangements. Furthermore, our findings can guide decisions about strategic housing of pairs in aviaries and identify solutions that mitigate the consequences of social crowding on reproductive success.

Personality studies are increasingly relevant and applicable to a broad range of conservation issues, including a role for selecting compatible mates in conservation breeding programs (CBPs). Choosing compatible breeding pairs is essential for maximizing reproductive success in CBPs, which provide assurance populations for species facing extinction and candidates for translocation to support wild populations. We investigated the value of caretaker‐assessed personality ratings of the critically endangered ‘Alalā (Hawaiian Crow, Corvus hawaiiensis) in predicting reproductive outcomes: nest quality, fertile egg production, and hatchability in the ‘Alalā CBP. Caretakers used well‐defined operational definitions to rate 22 personality traits for 69 male and 59 female ‘Alalā, achieving high inter‐rater agreement (ICC ≥ 0.85) for 8 traits – aggressive, bold/fearless, fearful, imprinted/abnormal, inept, submissive, territorial, and tendency to feather pluck (a stereotypic behavior) – used in a principal components analysis to distill intercorrelated variables into three principal components. While we did not find that personality influences nest quality or hatchability (based on limiting inferences to fixed effects with high relative importance scores; ≥0.8), we found some evidence that pairs with males that were more territorial/aggressive and fearful than their mates had a higher probability of egg fertilization, but there was substantial variability in this relationship, with confidence intervals overlapping zero. These personality traits may influence pair dynamics, enhancing compatibility, may predict better pair coordination on the nest, or both. Our results highlight the ability of caretakers to successfully identify ‘Alalā personality traits and provide some support for integrating personality into the pairing process; however, further research is needed to understand the value of ‘Alalā personality as a mate selection tool. The application of similar approaches to enhance CBP performance in other taxa is promising, but will require overcoming methodological challenges surrounding the complexity of data collection and interpretation of consistency among raters.

Supplemental feeding is a common soft‐release strategy for increasing settlement, survival, and breeding in animals after translocation. However, supplemental feeding can also hinder natural patterns of dispersal or influence social interactions. Some drawbacks of feeding can be mitigated if feeding stations can function as management tools for directing animals' movement, for example, by guiding them toward wild food resources or prospective territories while directing them away from potential threats, for example, predator hotspots or urban/agricultural centers. However, these effects may not work equally across individuals or habitat types. For species such as 'alalā ( Corvus hawaiiensis ), Hawaii's last living corvid, being able to manipulate space use via supplemental feeders could improve reintroduction outcomes. We determined if and how feeding stations influence a released population of 'alalā by strategically moving feeders across varying distances and habitat types, while measuring how quickly birds discovered new feeders and how their space use changed. We found that 'alalā discovered feeders more rapidly in closed as opposed to open canopy habitat, and feeder movement influenced how far 'alalā ranged, especially in afternoon periods. Sex, social network position, and individual home range size did not predict feeder discovery. These insights offer lessons for using supplemental feeding when managing reintroductions.

Translocation programs for endangered mammalian carnivores face numerous challenges, including the potential for lethal interactions between releasees and resident conspecifics. Here we evaluate whether familiarizing residents with the scent of releasees might be an effective strategy for reducing aggression following Tasmanian devil (Sarcophilus harrisii) translocation. Tasmanian devils live in loose social networks in which residents have overlapping home ranges and use communal latrines. In a controlled ex situ experiment, we first found that devils readily distinguished between the feces of familiar and unfamiliar conspecifics. Next, we swapped feces between devils slated for release and wild resident devils, seeding a random half of communal latrines in the wild with the feces of releasee prior to their release, and used motion-activated video cameras to record devil visits. Wild resident devil visitation frequency and olfactory communication behaviors initially increased at experimental latrine sites where feces were deposited but not at control sites. After release, the translocated devils used both types of latrine sites and spent more time investigating experimental sites, but investigatory and scent-marking behaviors of the wild resident devils decreased, suggesting that they had become familiar with the releasees through scent. We further show that Tasmanian devil latrine sites are strongly associated with ecotones and the presence of shrubs. These findings contribute to our understanding of Tasmanian devil scent ecology and suggest that devil translocations conducted into existing populations would benefit from familiarization through latrine scent manipulation. More broadly, our results suggest an important role for scent ecology in carnivore translocation programs. Significance statement: A conservation management action that is being trialed for endangered Tasmanian devils is to breed devils in human care and reinforce dwindling small resident populations through translocation. However, with limited social interactions, unfamiliar devils may interact aggressively, increasing injury and reducing translocation success. Scent communication is nearly ubiquitous in mammals and may be a prerequisite for management of social aggression. Almost nothing is known about devil scent ecology. Our discovery that devils become familiarized with conspecifics through feces, combined with findings that wild devils that are exposed to translocated devil scent in advance of release show reduced interest in scent-seeded latrines, even after new devils are released, suggests that devils familiarized through scent in advance of relocation may exhibit reduced aggression. These results provide an avenue for improving the success of translocations for devils and other at-risk solitary mammalian carnivores.

Pre‐release training is becoming a standard practice in conservation breeding and translocation programs for mammals and birds, but is still relatively neglected for herpetofauna, likely stemming from widespread beliefs that amphibians are “hard‐wired” and are thus predicted to benefit little from experiential learning. However, experience during development can drive both morphological and behavioral modifications that could benefit post‐translocation survival. Here, we developed an anti‐predator training program for the endangered mountain yellow‐legged frog Rana muscosa and evaluated its impact on morphometrics, developmental rates, behavior, and post‐release outcomes. Using a controlled, balanced factorial experimental design, we exposed individuals at two developmental stages (tadpoles and post‐metamorphic) to visual and olfactory cues from one of its principal predators, the two‐striped garter snake Thamnophis hammondii. We found that exposure to predators during the tadpole stage impacted tadpole development, morphology, and behavior. However, we found no evidence that post‐metamorphic behavior or post‐release outcomes were influenced by tadpole predator exposure, either on its own or in interaction with post‐metamorphic training treatments. Training of post‐metamorphic frogs, however, yielded evidence of learning, with downstream effects on behavior and apparent survival after release into the wild. Our findings produce novel insights on the value of anti‐predator training in amphibian conservation translocation programs, bolster recent evidence re‐evaluating the importance of learning and developmental experience for amphibian species, and provide guidance for selecting optimal developmental windows for training.

Mitigation translocations are increasing and if they are to fulfill their regulatory intent, the application of best‐practice principles to release strategy and monitoring is required. With an investment of 3 years, we engaged with stakeholders, including developers, to improve outcomes from mitigation translocations of an at‐risk species, the western burrowing owl Athene cunicularia hypugaea (BUOW). We evaluated the consequences of two primary translocation methods, displacement (i.e. exclusion from burrow) and translocation, against control owls, using a suite of success metrics focused on dispersal, survival and reproduction. We also tested the provision of visual and acoustic conspecific cues to dampen dispersal away from release sites. Within the displaced group, BUOW settled closer to the origin site if burrows were available nearby. Although translocated BUOW dispersed farther from the release site than displaced BUOW, this difference disappeared when conspecific cues were present. BUOW were 20 times more likely to settle at the release site when conspecifics or their cues were present. Translocating animals over longer distances (>17.5 km) reduced the incidence of BUOW returning to the origin site. When avoiding direct impacts to BUOW is not feasible, a determination of the most beneficial translocation method must be made, driven by site‐specific conditions and the feasibility of implementing best management practices. The known costs of translocation to survival may be offset by long‐term advantages such as the establishment of breeding populations inside protected areas. Mitigation translocations can benefit from carefully devised and tested hypotheses to determine what works and what does not; we advocate the increased use of evidence in mitigation translocation to guide management decisions and policies.