Photographic documentation of melanism in bobcats (Lynx rufus) in the Greater Everglades

We document the presence of bobcats (Lynx rufus) that demonstrate melanism in the Greater Everglades. The South Florida landscape is driven by a myriad of disturbance regimes particularly that of short fire intervals. We monitored 180 camera traps for 3 years and obtained 9503 photographs of bobcats 25 (<0.5%) of these detections included melanistic individuals. Our observations and historical accounts suggest melanism is a phenotype that persists, albeit it at an exceedingly low frequency, in bobcats in the region. While we do not know if the expression of melanism conferred a fitness benefit in our system, the vegetation structure that was characterized by frequently burned uplands and low-light and densely vegetated swamps produced conditions that may render a benefit from melanism through enhanced crypsis. The investigation of rare phenomenon in ecology is important yet difficult within a given field study, but reporting novel observations, like melanism in bobcats, allows for science to gain insight across studies that would not be otherwise possible.

Fire-driven animal evolution in the Pyrocene

Fire regimes are a major agent of evolution in terrestrial animals. Changing fire regimes and the capacity for rapid evolution in wild animal populations suggests the potential for rapid, fire-driven adaptive animal evolution in the Pyrocene. Fire drives multiple modes of evolutionary change, including stabilizing, directional, disruptive, and fluctuating selection, and can strongly influence gene flow and genetic drift. Ongoing and future research in fire-driven animal evolution will benefit from further development of generalizable hypotheses, studies conducted in highly responsive taxa, and linking fire-adapted phenotypes to their underlying genetic basis. A better understanding of evolutionary responses to fire has the potential to positively influence conservation strategies that embrace evolutionary resilience to fire in the Pyrocene.

Prey species increase activity in refugia free of terrestrial predators

The decline of terrestrial predator populations across the globe is altering top-down pressures that drive predator-prey interactions. However, a knowledge gap remains in understanding how removing terrestrial predators affects prey behavior. Using a bifactorial playback experiment, we exposed fox squirrels to predator (red-tailed hawks, coyotes, dogs) and non-predator control (Carolina wren) calls inside terrestrial predator exclosures, accessible to avian predators, and in control areas subject to ambient predation risk. Fox squirrels increased their use of terrestrial predator exclosures, a pattern that corresponded with 3 years of camera trapping. Our findings suggest fox squirrels recognized that exclosures had predictably lower predation risk. However, exclosures had no effect on their immediate behavioral response towards any call, and fox squirrels responded most severely to hawk predator calls. This study shows that anthropogenically driven predator loss creates predictably safer areas (refugia) that prey respond to proactively with increased use. However, the persistence of a lethal avian predator is sufficient to retain a reactive antipredator response towards an immediate predation threat. Some prey may benefit from shifting predator-prey interactions by gaining refugia without sacrificing a sufficient response towards potential predators.

Fire as a driver and mediator of predator-prey interactions

Both fire and predators have strong influences on the population dynamics and behaviour of animals, and the effects of predators may either be strengthened or weakened by fire. However, knowledge of how fire drives or mediates predator–prey interactions is fragmented and has not been synthesised. Here, we review and synthesise knowledge of how fire influences predator and prey behaviour and interactions. We develop a conceptual model based on predator–prey theory and empirical examples to address four key questions: (i) how and why do predators respond to fire; (ii) how and why does prey vulnerability change post‐fire; (iii) what mechanisms do prey use to reduce predation risk post‐fire; and (iv) what are the outcomes of predator–fire interactions for prey populations? We then discuss these findings in the context of wildlife conservation and ecosystem management before outlining priorities for future research. Fire‐induced changes in vegetation structure, resource availability, and animal behaviour influence predator–prey encounter rates, the amount of time prey are vulnerable during an encounter, and the conditional probability of prey death given an encounter. How a predator responds to fire depends on fire characteristics (e.g. season, severity), their hunting behaviour (ambush or pursuit predator), movement behaviour, territoriality, and intra‐guild dynamics. Prey species that rely on habitat structure for avoiding predation often experience increased predation rates and lower survival in recently burnt areas. By contrast, some prey species benefit from the opening up of habitat after fire because it makes it easier to detect predators and to modify their behaviour appropriately. Reduced prey body condition after fire can increase predation risk either through impaired ability to escape predators, or increased need to forage in risky areas due to being energetically stressed. To reduce risk of predation in the post‐fire environment, prey may change their habitat use, increase sheltering behaviour, change their movement behaviour, or use camouflage through cryptic colouring and background matching. Field experiments and population viability modelling show instances where fire either amplifies or does not amplify the impacts of predators on prey populations, and vice versa. In some instances, intense and sustained post‐fire predation may lead to local extinctions of prey populations. Human disruption of fire regimes is impacting faunal communities, with consequences for predator and prey behaviour and population dynamics. Key areas for future research include: capturing data continuously before, during and after fires; teasing out the relative importance of changes in visibility and shelter availability in different contexts; documenting changes in acoustic and olfactory cues for both predators and prey; addressing taxonomic and geographic biases in the literature; and predicting and testing how changes in fire‐regime characteristics reshape predator–prey interactions. Understanding and managing the consequences for predator–prey communities will be critical for effective ecosystem management and species conservation in this era of global change.

Gudgeon fish with and without genetically determined countershading coexist in heterogeneous littoral environments of an ancient lake

Countershading, characterized by a darker dorsal surface and lighter ventral surface, is common among many animals. This dorsoventral pigment polarity is often thought to be adaptive coloration for camouflage. By contrast, noncountershaded (melanistic) morphs often occur within a species due to genetic color polymorphism in terrestrial animals. However, the polymorphism with either countershaded or melanistic morphs is poorly known in wild aquatic animals. This study explored the genetic nature of diverged color morphs of a lineage of gudgeon fish (genus Sarcocheilichthys) in the ancient Lake Biwa and propose this system as a novel model for testing hypotheses of functional aspects of countershading and its loss in aquatic environments. This system harbors two color morphs that have been treated taxonomically as separate species; Sarcocheilichthys variegatus microoculus which occurs throughout the littoral zone and Sarcocheilichthys biwaensis which occurs in and around rocky areas. First, we confirmed that the divergence of dorsoventral color patterns between the two morphs is under strict genetic control at the levels of chromatophore distribution and melanin-related gene expression under common garden rearing. The former morph displayed sharp countershading coloration, whereas the latter morph exhibited a strong tendency toward its loss. The crossing results indicated that this divergence was likely controlled by a single locus in a two-allele Mendelian inheritance pattern. Furthermore, our population genomic and genome-wide association study analyses detected no genome-wide divergence between the two morphs, except for one region near a locus that may be associated with the color divergence. Thus, these morphs are either in a state of intraspecific color polymorphism or two incipient species. Evolutionary forces underlying this polymorphism appear to be associated with heterogeneous littoral environments in this lake. Future ecological genomic research will provide insight into adaptive functions of this widespread coloration, including the eco-evolutionary drivers of its loss, in the aquatic world.

Aposematic signaling and seasonal variation in dorsal pelage in a venomous mammal

In mammals, colouration patterns are often related to concealment, intraspecific communication, including aposematic signals, and physiological adaptations. Slow lorises (Nycticebus spp.) are arboreal primates native to Southeast Asia that display stark colour contrast, are highly territorial, regularly enter torpor, and are notably one of only seven mammal taxa that possess venom. All slow loris species display a contrasting stripe that runs cranial-caudally along the median sagittal plane of the dorsum. We examine whether these dorsal markings facilitate background matching, seasonal adaptations, and intraspecific signaling. We analyzed 195 images of the dorsal region of 60 Javan slow loris individuals (Nycticebus javanicus) from Java, Indonesia. We extracted greyscale RGB values from dorsal pelage using ImageJ software and calculated contrast ratios between dorsal stripe and adjacent pelage in eight regions. We assessed through generalized linear mixed models if the contrast ratio varied with sex, age, and seasonality. We also examined whether higher contrast was related to more aggressive behavior or increased terrestrial movement. We found that the dorsal stripe of N. javanicus changed seasonally, being longer and more contrasting in the wet season, during which time lorises significantly increased their ground use. Stripes were most contrasting in younger individuals of dispersal age that were also the most aggressive during capture. The dorsal stripe became less contrasting as a loris aged. A longer stripe when ground use is more frequent can be related to disruptive colouration. A darker anterior region by younger lorises with less fighting experience may allow them to appear larger and fiercer. We provide evidence that the dorsum of a cryptic species can have multimodal signals related to concealment, intraspecific communication, and physiological adaptations.