Neo-tropical felid activity patterns in relation to potential prey and intraguild competitors in the Calakmul Biosphere Reserve,Mexico

Predator behaviors influence, and are influenced by, prey and competitor behaviors. Jaguars (Panthera onca), pumas (Puma concolor), and ocelots (Leopardus pardalis) coexist throughout their geographic range as the three largest predators in a multi-predator community across diverse environments. This study tested for non-random segregation and overlap in the activity patterns of these felids and their shared prey in the southern buffer zone of the Calakmul Biosphere Reserve, in southern Mexico, using camera traps during February to August 2019. We detected little temporal segregation between the nocturnal activities of jaguars, pumas, and ocelots, although pumas were more active closer to dawn. Jaguars had low activity overlap with species likely to be common prey, whereas ocelots had high overlap with their potential prey. Pumas displayed finer-scale similarities in activity with species likely to be common prey. In an understudied area of conservation importance, this study shows that temporal segregation is an unlikely mechanism of coexistence. Further research should incorporate spatio-temporal avoidance and dietary differences to improve our understanding of the mechanisms that drive coexistence between generalist species in a diverse assemblage of threatened felids. Abstract in Spanish is available with online material.     

Food Habits and Livestock Depredation of Sympatric Jaguars and Pumas in the Iguaçu National Park Area, South Brazil

Understanding coexistence between sympatric felines with similar body sizes, such as jaguars Panthera onca and pumas Puma concolor , requires knowledge of the way these predators consume and partition food resources. Yet the importance of livestock predation on jaguar and puma coexistence is poorly known. I investigated food habits and patterns of livestock depredation of jaguar and pumas in the Iguaçu National Park (INP) in southern Brazil. From 1997 to 2001, I collected scats opportunistically on trails and roads in INP and visited ranches on the border of INP. I found that jaguars relied mostly on large and medium-sized wild prey species, while pumas concentrated on medium-sized prey species. Livestock was the fifth most frequent prey found in jaguar scats but the most important one in terms of biomass consumed. Jaguar and puma diets differed significantly when all prey items were compared and also when livestock was excluded from the jaguar diet. Jaguar predation on livestock was considerably higher than predation by pumas. However, predation was not substantial relative to availability of livestock, and cattle likely constitute an alternative source of prey for jaguars. Degree of diet overlap between jaguar and puma in INP suggests that coexistence was likely driven by exploitative competition through some degree of food partitioning. My results highlight the importance of more actions toward increasing numbers of large ungulates to preserve the population of jaguars in INP.     

American marten and fisher do not segregate in space and time during winter in a mixed‐forest system

Understanding the mechanisms of coexistence between ecologically similar species is an important issue in ecology. Carnivore coexistence may be facilitated by spatial segregation, temporal avoidance, and differential habitat selection. American martens Martes americana and fishers Pekania pennanti are medium‐sized mustelids that occur sympatrically across portions of North America, yet mechanisms of coexistence between the two species are not fully understood. We assessed spatial and temporal partitioning in martens and fishers in the Upper Peninsula of Michigan, USA, using camera trap data collected during winter 2013–2015. To investigate spatial segregation, we used a dynamic occupancy model to estimate species’ occupancy probabilities and probabilities of persistence and colonization as a function of covariates and yearly occupancy probability for the other species. Temporal segregation was assessed by estimating diel activity overlap between species. We found weak evidence of spatial or temporal niche partitioning of martens and fishers. There was high overlap in forest cover selection, and both marten and fisher occupancy were positively correlated with deciduous forests (excluding aspen [Populus tremuloides]). There was strong temporal overlap (; CI = 0.79–0.82) with both species exhibiting largely crepuscular activity patterns. Co‐occurrence of martens and fishers appears to be facilitated by mechanisms not investigated in this study, such as partitioning of snow features or diet. Our results add additional insights into resource partitioning of mesocarnivores, but further research is required to enhance our understanding of mechanisms that facilitate marten and fisher coexistence.     

In the absence of a “landscape of fear”: How lions,hyenas, and cheetahs coexist

Aggression by top predators can create a “landscape of fear” in which subordinate predators restrict their activity to low‐risk areas or times of day. At large spatial or temporal scales, this can result in the costly loss of access to resources. However, fine‐scale reactive avoidance may minimize the risk of aggressive encounters for subordinate predators while maintaining access to resources, thereby providing a mechanism for coexistence. We investigated fine‐scale spatiotemporal avoidance in a guild of African predators characterized by intense interference competition. Vulnerable to food stealing and direct killing, cheetahs are expected to avoid both larger predators; hyenas are expected to avoid lions. We deployed a grid of 225 camera traps across 1,125 km² in Serengeti National Park, Tanzania, to evaluate concurrent patterns of habitat use by lions, hyenas, cheetahs, and their primary prey. We used hurdle models to evaluate whether smaller species avoided areas preferred by larger species, and we used time‐to‐event models to evaluate fine‐scale temporal avoidance in the hours immediately surrounding top predator activity. We found no evidence of long‐term displacement of subordinate species, even at fine spatial scales. Instead, hyenas and cheetahs were positively associated with lions except in areas with exceptionally high lion use. Hyenas and lions appeared to actively track each, while cheetahs appear to maintain long‐term access to sites with high lion use by actively avoiding those areas just in the hours immediately following lion activity. Our results suggest that cheetahs are able to use patches of preferred habitat by avoiding lions on a moment‐to‐moment basis. Such fine‐scale temporal avoidance is likely to be less costly than long‐term avoidance of preferred areas: This may help explain why cheetahs are able to coexist with lions despite high rates of lion‐inflicted mortality, and highlights reactive avoidance as a general mechanism for predator coexistence.     

Interspecific interactions between wild felids vary across scales and levels of urbanization

Ongoing global landscape change resulting from urbanization is increasingly linked to changes in species distributions and community interactions. However, relatively little is known about how urbanization influences competitive interactions among mammalian carnivores, particularly related to wild felids. We evaluated interspecific interactions between medium‐ and large‐sized carnivores across a gradient of urbanization and multiple scales. Specifically, we investigated spatial and temporal interactions of bobcats and pumas by evaluating circadian activity patterns, broad‐scale seasonal interactions, and fine‐scale daily interactions in wildland–urban interface (WUI), exurban residential development, and wildland habitats. Across levels of urbanization, interspecific interactions were evaluated using two‐species and single‐species occupancy models with data from motion‐activated cameras. As predicted, urbanization increased the opportunity for interspecific interactions between wild felids. Although pumas did not exclude bobcats from areas at broad spatial or temporal scales, bobcats responded behaviorally to the presence of pumas at finer scales, but patterns varied across levels of urbanization. In wildland habitat, bobcats avoided using areas for short temporal periods after a puma visited an area. In contrast, bobcats did not appear to avoid areas that pumas recently visited in landscapes influenced by urbanization (exurban development and WUI habitat). In addition, overlap in circadian activity patterns between bobcats and pumas increased in exurban development compared to wildland habitat. Across study areas, bobcats used sites less frequently as the number of puma photographs increased at a site. Overall, bobcats appear to shape their behavior at fine spatial and temporal scales to reduce encounters with pumas, but residential development can potentially alter these strategies and increase interaction opportunities. We explore three hypotheses to explain our results of how urbanization affected interspecific interactions that consider activity patterns, landscape configuration, and animal scent marking. Altered competitive interactions between animals in urbanized landscapes could potentially increase aggressive encounters and the frequency of disease transmission.     

Fine‐scale coexistence between Mediterranean mesocarnivores is mediated by spatial,temporal, and trophic resource partitioning

1. The partition of the ecological niche can enhance the coexistence of predators due to differences in how they exploit three main resources: food, space, and time, the latter being an axis that often remains unexplored.
2. We studied niche segregation in a Mediterranean mesocarnivore community composed by Vulpes vulpes, Genetta genetta, Meles meles, and Herpestes ichneumon, addressing simultaneously different niche axes: the temporal, trophic, and spatial axes.
3. We assessed temporal segregation between mesopredators and prey and between potential competitors, using camera trap data between 2018 and 2020 in a Mediterranean landscape in Southern Spain. We deployed camera traps in 35 stations in three sites with varying vegetation cover within Doñana National Park. We further examined the spatial overlap in activity centers and trophic preferences between potential competitors using diet information from studies performed in the study area.
4. We found an overall temporal segregation between trophic generalist species, with species showing higher temporal overlap differing in their trophic preferences and/or showing limited spatial overlap. Furthermore, we observed an overall high overlap between the activity patterns of predators and their major prey in the area (the common genet vs. small mammals and the red fox vs. European rabbit).
5. Our study suggests that coexistence of the different species that compose the mesocarnivore assemblage in Mediterranean landscapes can be facilitated by subtle differences along the three main niche axes, with temporal segregation being a most pronounced mechanism. Our findings reinforce the idea that the coexistence mechanisms underlying community structure are multidimensional.

     

Dietary partitioning promotes the coexistence of planktivorous species on coral reefs

Theories involving niche diversification to explain high levels of tropical diversity propose that species are more likely to co‐occur if they partition at least one dimension of their ecological niche space. Yet, numerous species appear to have widely overlapping niches based upon broad categorizations of resource use or functional traits. In particular, the extent to which food partitioning contributes to species coexistence in hyperdiverse tropical ecosystems remains unresolved. Here, we use a molecular approach to investigate inter‐ and intraspecific dietary partitioning between two species of damselfish (Dascyllus flavicaudus, Chromis viridis) that commonly co‐occur in branching corals. Species‐level identification of their diverse zooplankton prey revealed significant differences in diet composition between species despite their seemingly similar feeding strategies. Dascyllus exhibited a more diverse diet than Chromis, whereas Chromis tended to select larger prey items. A large calanoid copepod, Labidocera sp., found in low density and higher in the water column during the day, explained more than 19% of the variation in dietary composition between Dascyllus and Chromis. Dascyllus did not significantly shift its diet in the presence of Chromis, which suggests intrinsic differences in feeding behaviour. Finally, prey composition significantly shifted during the ontogeny of both fish species. Our findings show that levels of dietary specialization among coral reef associated species have likely been underestimated, and they underscore the importance of characterizing trophic webs in tropical ecosystems at higher levels of taxonomic resolution. They also suggest that niche redundancy may not be as common as previously thought.     

Dietary overlap and seasonality in three species of mormoopid bats from a tropical dry forest

Competing hypotheses explaining species’ use of resources have been advanced. Resource limitations in habitat and/or food are factors that affect assemblages of species. These limitations could drive the evolution of morphological and/or behavioural specialization, permitting the coexistence of closely related species through resource partitioning and niche differentiation. Alternatively, when resources are unlimited, fluctuations in resources availability will cause concomitant shifts in resource use regardless of species identity. Here, we used next‐generation sequencing to test these hypotheses and characterize the diversity, overlap and seasonal variation in the diet of three species of insectivorous bats of the genus Pteronotus. We identified 465 prey (MOTUs) in the guano of 192 individuals. Lepidoptera and Diptera represented the most consumed insect orders. Diet of bats exhibited a moderate level of overlap, with the highest value between Pteronotus parnellii and Pteronotus personatus in the wet season. We found higher dietary overlap between species during the same seasons than within any single species across seasons. This suggests that diets of the three species are driven more by prey availability than by any particular predator‐specific characteristic. P. davyi and P. personatus increased their dietary breadth during the dry season, whereas P. parnellii diet was broader and had the highest effective number of prey species in all seasons. This supports the existence of dietary flexibility in generalist bats and dietary niche overlapping among groups of closely related species in highly seasonal ecosystems. Moreover, the abundance and availability of insect prey may drive the diet of insectivores.     

The dietary basis for temporal partitioning: food habits of coexisting Acomys species

Two rodent species of the genus Acomys coexist on rocky terrain in the southern deserts of Israel. The common spiny mouse (A. cahirinus) is nocturnally active whereas the golden spiny mouse (A. russatus) is diurnally active. An early removal study suggested that competition accounts for this pattern of temporal partitioning: the golden spiny mouse is forced into diurnal activity by its congener. Theoretically, temporal segregation should facilitate coexistence if the shared limiting resources differ at different times (primarily among predators whose prey populations have activity rhythms), or if they are renewed within the period of the temporal segregation. We studied food preferences of the two Acomys species in a controlled cafeteria experiment in order to assess resource overlap and the potential for competition for food between the two species. We found no significant difference in food preferences between species. The dietary items preferred by both were arthropods. We also carried out a seasonal study of the percentage and identity of arthropods taken in the field by individuals of the two species. Individuals of both species took on annual average a high percentage of arthropods in their diets. Seasonal diet shifts reflect seasonal abundance of arthropods at Ein Gedi during day and night. Diurnal activity may also reduce interspecific interference competition between A. russatus and A. cahirinus. However, the strong interspecific dietary overlap in food preference, the heavy reliance on arthropods in spiny mouse diets, and the seasonal and circadian differences in arthropod consumption suggest that prey partitioning may be a viable mechanism of coexistence in this system. Received: 6 July 1998 / Accepted: 10 May 1999     

Spatial ecology of jaguars,pumas, and ocelots: a review of the state of knowledge

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Spatial and temporal overlap of caracal and serval in Serengeti National Park,Tanzania

Understanding activity and habitat use are important for identifying mechanisms facilitating species co-occurrence. We studied habitat use and activity patterns of caracals (Caracal caracal) and servals (Leptailurus serval), primarily nocturnal, mid-sized felids that prey extensively on small mammals and co-occur in portions of sub-Saharan Africa. Spatial and temporal patterns of segregation were investigated in a 1,085-km² area of Serengeti National Park, Tanzania from 2010–2012. We used occupancy analysis to quantify habitat use and kernel density estimators and Mardia–Watson–Wheleer tests to analyse activity patterns. We found evidence for habitat divergence but high temporal overlap between species. Servals selected for grassland and avoided shrubland and wooded grassland. In contrast, the findings showed that caracals avoided grassland and woodland–shrubland; however, 73% of caracals were detected in wooded grassland. Overall, caracals and servals co-occurred independently, Species Interaction Factor, (phi = 1). This indicates that differential use of habitats in part facilitated coexistence of caracals and servals. Proper management of the declining grasslands including other habitats are recommended to facilitate continued coexistence. Additional studies, including feeding ecology, would be important to further understand mechanisms facilitating coexistence between caracals and servals.     

Using dive behavior and active acoustics to assess prey use and partitioning by fin and humpback whales near Kodiak Island,Alaska

Near the Kodiak Archipelago, fin (Balaenoptera physalus) and humpback (Megaptera novaeangliae) whales frequently overlap spatially and temporally. The Gulf Apex Predator‐prey study (GAP) investigated the prey use and potential prey partitioning between these sympatric species by combining concurrent analysis of vertical whale distribution with acoustic assessment of pelagic prey. Acoustic backscatter was classified as consistent with either fish or zooplankton. Whale dive depths were determined through suction cup tags. Tagged humpback whales (n = 10) were most often associated with distribution of fish, except when zooplankton density was very high. Associations between the dive depths of tagged fin whales (n = 4) and the vertical distribution of either prey type were less conclusive. However, prey assessment methods did not adequately describe the distribution of copepods, a potentially significant resource for fin whales. Mean dive parameters showed no significant difference between species when compared across all surveys. However, fin whales spent a greater proportion of dive time in the foraging phase than humpbacks, suggesting a possible difference in foraging efficiency between the two. These results suggest that humpback and fin whales may target different prey, with the greatest potential for diet overlap occurring when the density of zooplankton is very high.     

Habitat Use by Sympatric Jaguars and Pumas Across a Gradient of Human Disturbance in Belize

Jaguars (Panthera onca) and pumas (Puma concolor) are sympatric across the entire jaguar range, where they coexist in increasingly fragmented landscapes under threat of persecution mainly in response to livestock predation. Pumas are known to inhabit a greater variety of natural habitats than jaguars, but little is known about the influence of anthropogenic factors on the coexistence of these two similar-sized cats. This study compares habitat use of jaguars and pumas in Belize, Central America, using 1380 jaguar and puma photo captures from 3 yr of camera trapping, comprising 64–74 individual jaguars and an unknown number of pumas. Jaguars and pumas did not differ in their use of a large block of relatively homogenous secondary rain forest. However, pumas were scarce outside this forest block, whereas jaguars were detected throughout the human-influenced landscape. Reasons for this discrepancy may include differential tolerance to human disturbance, and resource limitation for pumas outside the forest block. Intra-specific variation in jaguar activity in the form of sex-dependent habitat use was detected across the landscape. Male jaguars were detected at more locations than female jaguars and more frequently at each location, with a declining difference from a 50-fold greater detection in the protected forest, through forest buffer, savannah, pastures, to negligible difference in the disturbed forest.     

Cryptic differences in colour among Müllerian mimics: how can the visual capacities of predators and prey shape the evolution of wing colours?

Antagonistic interactions between predators and prey often lead to co‐evolution. In the case of toxic prey, aposematic colours act as warning signals for predators and play a protective role. Evolutionary convergence in colour patterns among toxic prey evolves due to positive density‐dependent selection and the benefits of mutual resemblance in spreading the mortality cost of educating predators over a larger prey assemblage. Comimetic species evolve highly similar colour patterns, but such convergence may interfere with intraspecific signalling and recognition in the prey community, especially for species involved in polymorphic mimicry. Using spectrophotometry measures, we investigated the variation in wing coloration among comimetic butterflies from distantly related lineages. We focused on seven morphs of the polymorphic species Heliconius numata and the seven corresponding comimetic species from the genus Melinaea. Significant differences in the yellow, orange and black patches of the wing were detected between genera. Perceptions of these cryptic differences by bird and butterfly observers were then estimated using models of animal vision based on physiological data. Our results showed that the most strikingly perceived differences were obtained for the contrast of yellow against a black background. The capacity to discriminate between comimetic genera based on this colour contrast was also evaluated to be higher for butterflies than for birds, suggesting that this variation in colour, likely undetectable to birds, might be used by butterflies for distinguishing mating partners without losing the benefits of mimicry. The evolution of wing colour in mimetic butterflies might thus be shaped by the opposite selective pressures exerted by predation and species recognition.     

Temporal partitioning of activity: rising and falling top‐predator abundance triggers community‐wide shifts in diel activity

Top predators cause avoidance behaviours in competitors and prey, which can lead to niche partitioning and facilitate coexistence. We investigate changes in partitioning of the temporal niche in a mammalian community in response to both the rapid decline in abundance of a top predator and its rapid increase, produced by two concurrent natural experiments: 1) the severe decline of the Tasmanian devil due to a transmissible cancer, and 2) the introduction of Tasmanian devils to an island, with subsequent population increase. We focus on devils, two mesopredators and three prey species, allowing us to examine niche partitioning in the context of intra‐ and inter‐specific competition, and predator–prey interactions. The most consistent shift in temporal activity occurred in devils themselves, which were active earlier in the night at high densities, presumably because of heightened intraspecific competition. When devils were rare, their closest competitor, the spotted‐tailed quoll, increased activity in the early part of the night, resulting in increased overlap with the devil's temporal niche and suggesting release from interference competition. The invasive feral cat, another mesopredator, did not shift its temporal activity in response to either decreasing or increasing devil densities. Shifts in temporal activity of the major prey species of devils were stronger in response to rising than to falling devil densities. We infer that the costs associated with not avoiding predators when their density is rising (i.e. death) are higher than the costs of continuing to adopt avoidance behaviours as predator densities fall (i.e. loss of foraging opportunity), so rising predator densities may trigger more rapid shifts. The rapid changes in devil abundance provide a unique framework to test how the non‐lethal effects of top predators affect community‐wide partitioning of temporal niches, revealing that this top predator has an important but varied influence on the diel activity of other species.     

Intra‐ and interspecific interactions between aphidophagous ladybirds: the role of prey in predator coexistence

Cannibalism (CANN) and intraguild predation (IGP) may provide energy and nutrients to individuals and eliminate potential competitors. These negative competitive interactions could also affect the coexistence of predatory species. The co‐occurrence of aphidophagous ladybird species in crops creates opportunities for CANN and IGP, especially when aphids become scarce. The Lotka–Volterra model predicts the coexistence of two species if intraspecific competition is stronger than interspecific interference interactions. Cycloneda sanguinea L. and Eriopis connexa (Germar) (both Coleoptera: Coccinellidae) coexist in sweet pepper crops in La Plata (Argentina) consuming mainly Myzus persicae (Sulzer) (Hemiptera: Aphididae). The present study used laboratory experiments to estimate levels of CANN and IGP by adults and larvae on eggs, and by adults on larvae, in both the presence and absence of prey (i.e., M. persicae), to explain the effect of prey on coexistence of these two predators. Levels of CANN by C. sanguinea and E. connexa were high in the absence of aphids, and decreased when prey was present. Intraguild predation was bidirectional and asymmetric. Adults and larvae of E. connexa were more voracious IG predators of C. sanguinea than vice versa, the former being the stronger IG predator and interference competitor. Eriopis connexa always won when larvae of the same instar were compared, whereas the larger larva always won when larvae were of different instars, regardless of species. In the presence of prey, CANN by both species decreased, but IGP by E. connexa on C. sanguinea remained high, suggesting that E. connexa could displace C. sanguinea via interspecific interference competition. Other factors potentially affecting the coexistence of C. sanguinea and E. connexa in sweet pepper crops are discussed.     

Realized trophic niche driven by apparent competition: an example with marsupials

According to apparent competition theory, the co‐occurrence of two species that share the same predators appears to affect each other's population growth and abundance. However, due to habitat loss and over‐hunting, top predators are being made rare worldwide. Considering that apparent competitors share similar resources, we would expect the absence of top predators to reflect in changes on prey realized trophic niches. To test our hypothesis, we developed a model to predict the abundance ratio of apparent competitor species based on changes in their realized trophic niches. We tested our model against field data on the Neotropical marsupials Didelphis aurita and Metachirus nudicaudatus. Our results revealed that D. aurita and M. nudicaudatus are two species under apparent competition and their realized trophic niche and diet overlap change according to the presence of top predators. The model was able to predict the actual relative abundances of D. aurita and M. nudicaudatus in the three empirical studies analyzed. Our study presents quantitative support to the apparent competition theory; however, the model's applications to other groups still need to be verified. Additionally, our study shows that the lack of top predators has consequences on the realized trophic niche of their prey, and therefore, we reinforce that conservation plans need to focus on the effects of top predator loss on ecosystems.     

Prey Spectra of Jaguar (Panthera onca) and Puma (Puma concolor) in Tropical Forests of Mexico

At the Calakmul Biosphere Reserve in Campeche, Mexico, the prey spectra of sympatric jaguars (Panthera onca) and pumas (Puma concolor) were studied by examination of their scats. 10 vertebrate species were identified for jaguars and 7 for pumas, mainly mammals and some birds. Based on these diet analyses, we conclude that jaguars and pumas coexist at Calakmul by means of different food habits.     

Capture efficiency and trophic adaptations of a specialist and generalist predator: A comparison

Specialist true predators are expected to exhibit higher capture efficiencies for the capture of larger and dangerous prey than generalist predators due to their possession of specialized morphological and behavioral adaptations. We used an araneophagous spider (Lampona murina) and a generalist spider (Drassodes lapidosus) as phylogenetically related model species and investigated their realized and fundamental trophic niches and their efficacy with respect to prey capture and prey handling. The trophic niche of both species confirmed that Lampona had a narrow trophic niche with a predominance of spider prey (including conspecifics), while the niche of Drassodes was wide, without any preference. DNA analysis of the gut contents of Lampona spiders collected in the field revealed that spiders form a significant part of its natural diet. Lampona captured significantly larger prey than itself and the prey captured by Drassodes. As concerns hunting strategy, Lampona grasped the prey with two pairs of legs possessing scopulae, whereas Drassodes immobilized prey with silk. Lampona possess forelegs equipped with scopulae and a thicker cuticle similar to other nonrelated araneophagous spiders. Lampona fed for a longer time and extracted more nutrients than Drassodes. We show that specialized behavioral and morphological adaptations altogether increase the hunting efficiency of specialists when compared to generalists.     

Environmentally-induced shifts in behavior intensify indirect competition by an invasive gecko in Mauritius

Most recorded extinctions have occurred on oceanic islands, mainly as a result of introduced mammalian predators. The impact of introduced non-mammalian competitors, however, is poorly understood. The house gecko, Hemidactylus frenatus, is one of the most successful invasive reptiles and has been implicated in the decline of endemic geckos and other taxa on a number of tropical and subtropical islands. We investigated the patterns of niche utilization between the house gecko and endemic ornate day gecko, Phelsuma ornata, in Mauritius, two species which were not believed to compete because they had different diel activity periods. The dietary and temporal niche partitioning of the two species were examined in relation to seasonal invertebrate prey abundance for three seasons. Dietary overlap between the two species was least when prey abundance was lowest and temporal overlap in activity greatest. Exploitative competition was therefore inferred, whereby changes in dietary overlap were attributed to shifts in prey selection by the day, but not the house, gecko, which was hypothesized to deplete prey. The compensatory response of the day gecko may have been to increase its tendency for cannibalism, such that the smaller house gecko was indirectly responsible for population reduction of its larger competitor. This is the first study to show how an invasive nocturnal gecko may be affecting a predominantly diurnal species.