Predator Guild Research Articles

Shared Insights across the Ecology of Coral Reefs and African Savannas: Are Parrotfish Wet Wildebeest?

Abstract Comparison across terrestrial and aquatic ecosystems facilitates a broader understanding of ecological patterns. Although meta-analyses are important for quantitative synthesis across ecosystems, detailed comparisons of natural history and species interactions also illuminate convergence among systems. We compare the ecology of superficially dissimilar African savannas and coral reefs via shared characteristics including: (1) hyperdiverse guilds of large vertebrate herbivores and predators, (2) similar mechanisms driving positive feedback loops between herbivory and primary production, (3) similar roles of disturbance and herbivory in mediating ecosystem state, and (4) numerous smaller vertebrate and invertebrate species that underpin diversity and ecosystem processes. Our goal in comparing the natural history and ecology of these ecosystems is to facilitate others in finding their own comparative systems. We encourage scientists, especially early-career scientists, to explore ecosystems other than their primary focus. Whatever your ecosystem of study, examining the ecology of its analog in another environment may enliven your career.

Occurrence of Ants (Hymenoptera: Formicidae) in both Leaf Litter and Twigs in Atlantic Forest

Twigs in the litter derived from the fragmentation of tree branches form one microhabitat, where entire colonies of ants, both leaf litter and arboreal species, can be found. The objective was to survey ant species that are presente in both the leaf litter and twigs simultaneously. We describe the nest type, the social structure of the colonies and the trophic guild membership of these species. Samples were collected from 10 preserved fragments of Brazilian Atlantic forest. We used Berlese funnels to collect leaf litter ants and manual collection for twig ants. We recorded 80 ant species; 60 species were in leaf litter samples and 35 species were in twigs. Of the total species, only 15 (20%) occurred simultaneously in the leaf litter and in twigs. Of these species, Gnamptogenys striatula, Pheidole sarcina, P. sospes and Solenopsis sp. 2 were the most frequent among leaf litter dwellers, and Myrmelachista catharinae was the most common arboreal species. Most of these belonged to generalista and predator guilds, with “polydomous nests” and colonies monogynous.

The buoyancy-based biotope axis of the evolutionary radiation of Antarctic cryonotothenioid fishes

In the absence of any prior comprehensive analysis, I evaluate divergence along the biotope axis in the habitat stage of the evolutionary radiation of Antarctic cryonotothenioids. I utilize the available percentage buoyancy (%B) measurements as habitat proxies for recognition of the pelagic, semipelagic, demersal, and benthic biotopes that include, respectively, 5%, 10%, 73%, and 12% of the 59 species and 1749 specimens in the study. The majority of species retain the ancestral demersal biotope of Eleginops maclovinus, and this probably enhances ecological plasticity. Divergence into the pelagic biotope is the most distinctive organismal feature of the radiation and, although only 5% of species are pelagic, this biotope is not depauperate in global comparisons. Pelagic or potentially pelagic species are Dissostichus mawsoni, D. eleginoides, Pleuragramma antarctica, Aethotaxis mitopteryx, and Gvozdarus svetovidovi. Small ontogenetic changes in %B with growth are typical; however, this is extensive in D. mawsoni, a species with the potential to transition through benthic to pelagic biotopes over ontogeny. Occupation of the pelagic biotope by large D. mawsoni may be impermanent as it is lipid-dependent, a contingency reliant on the availability of P. antarctica as prey. In unusual conditions, the specialized sacs of P. antarctica can also yield their lipid for metabolism with possible loss of buoyancy. Pelagic species are inordinately important in the food web. In the southwestern Ross Sea a guild of large mammalian and avian predators, which includes D. mawsoni, is reliant on lipid-rich, energy-dense cryonotothenioid prey. This includes asymmetrical intraguild predation on D. mawsoni, with P. antarctica as a basal resource for the guild.

Fluctuations in field vole abundance indirectly influence red grouse productivity via a shared predator guild

Changes in the abundance of one prey species may indirectly affect other prey species by triggering responses in generalist predators. Here we examine relationships between two prey species that do not compete directly, the field vole Microtus agrestis, a common rodent with fluctuating populations, and the red grouse Lagopus lagopus scotica, a gamebird inhabiting open moorland, during a 27-year study on a moor in south-west Scotland. First, we test whether vole abundance was related to grouse density and demographic rates. Second, we test whether vole abundance was related to abundance indices of four common predators of both voles and grouse (red fox Vulpes vulpes, weasel Mustela nivalis, hen harrier Circus cyaneus and common buzzard Buteo buteo). Third, we test whether these vole–grouse and vole–predator relationships differ in relation to grouse management, which includes the culling of foxes and weasels. We found no association between vole abundance and grouse densities, adult summer survival or nesting success. However, the ratio of young grouse per adult and the proportion of female grouse with broods in July were negatively associated with field vole abundance, suggesting increased predation of grouse chicks in years with high vole abundance. Fox indices showed a weak positive association with vole abundance when their numbers were not controlled, whilst weasel indices showed no relationship with voles. The numbers of breeding hen harriers and buzzards were also not associated with vole abundance, but the number of buzzard sightings was higher when voles were more plentiful. Our results are consistent with a negative interaction between field voles and red grouse chick survival in a pattern expected for apparent competition. Although the underlying mechanisms could not be disentangled, this interaction may be at least partly mediated by rodent-hunting raptors such as buzzards and, in periods without grouse management, foxes.

Testing the hypothesis of an impoverished predator guild in the Early Miocene ecosystems of Patagonia: An analysis of meat availability and competition intensity among carnivores

The lower Miocene Santa Cruz Formation (dated to ~18–16 Ma) of Southern Patagonia, Argentina, preserves rich vertebrate faunas, which are representative of communities that existed prior to the Great American Biotic Interchange (GABI). Some previous researchers have hypothesized that these pre-GABI faunas had a low richness of mammalian carnivores (an impoverished predator guild), while others argue for a predator/prey ratio similar to those of recent communities. In this paper, we analyze faunas from the lower part of the Santa Cruz Formation (FL 1–7) using a methodology that allows us to quantify (i) the meat resources that were available to the secondary consumers of the palaeocommunity; and (ii) the competition intensity for these resources. In our modeling, we considered different scenarios related to meat consumption, including the possibility that several taxa had a scavenging behavior, and also differences in mortality rates between young and adult prey. Our results provide estimates of the nutritional requirements from the predator/scavenger guild under maximum and minimum quantities of meat offered by the prey community, which indicate the presence of a well-balanced palaeocommunity. Moreover, the competition indices point to a relatively high level of competition for prey of small-to-medium size, although competition for resources from large mammal prey was rather low. This suggests that the predator/scavenger guild was not impoverished, although there were insufficient carnivore species to fully consume the megaherbivore biomass.

Survival and Cause-Specific Mortality of Neonate Elk in a Unique Predator Environment in the Black Hills of South Dakota and Wyoming, U.S.A.

We conducted a 2 y study of survival and cause-specific mortality of elk (Cervus elaphus) calves to determine the current status of elk occupying the southwestern region of the Black Hills National Forest, South Dakota and eastern Wyoming. We captured and fit 71 calves ≤10 d of age with expandable radiocollars during summer 2012 (n = 37) and 2013 (n = 34). We used known-fate analysis in Program MARK to estimate summer (15 May–25 Sep.) and annual (12 mo) survival for elk calves. The top model for summer survival was {S1–2wk,3–20wk} indicating mortality during 1–2 wk of age and 3–20 wk of age best explained survival; overall probability of surviving 20 wk was 0.79 (95% CI = 0.68–0.88). For annual (12 mo) survival, model {Sbirthweight} had the lowest AICc value indicating birth weight of elk calves best explained survival as heavier born calves had a higher probability of survival. The overall probability a calf survived to 12 mo of age was 0.75 (95% CI = 0.61–0.84). Cougar (Puma concolor) predation accounted for 81% of mortalities; remaining mortalities were from starvation (6.3%, n = 1) and unknown causes (6.3%, n = 1). Our results document high survival for calves likely due to productive habitats, an ecosystem-specific predator guild, and high alternative prey.

Spatial and temporal overlaps between leopards (Panthera pardus) and their competitors in the African large predator guild

AbstractUnderstanding the mechanisms facilitating coexistence within species assemblages is a key consideration for conservation as intact assemblages are necessary for maintaining full ecosystem function. The African large predator guild represents one of the few remaining functionally intact large predator assemblages on Earth, and as such, represents a unique study system to understand competitive interactions. Yet, relatively little is known of the coexistence mechanisms between some of its intermediately sized members, particularly leopards (Panthera pardus). Here, we use overlapping spatio‐temporal activity and GPS data on lions (Panthera leo), leopards, African wild dogs (Lycaon pictus) and cheetahs (Acinonyx jubatus) to examine spatial interactions and temporal partitioning between leopards and other guild members in northern Botswana. We found that at the population level, male leopard space use and activity patterns were largely unaffected by intraguild competitors. Leopards showed minimal movement coherence with competitors (avoidance or attraction) when moving through areas of home ranges shared with intraguild species. Moreover, we found evidence to support the hypothesis that guild species’ activity patterns are primarily driven by light availability rather than predator avoidance. Our results suggest predator avoidance has a limited impact on broad‐scale leopard spatio‐temporal niches, with aspects of the leopards’ ecology and life history likely facilitating its ability to thrive in close proximity to competitors. Considered alongside other studies, our results suggest that landscape‐level approaches to conservation may be suitable for aiding leopard conservation.

Trophic redundancy and predator size class structure drive differences in kelp forest ecosystem dynamics.

Ecosystems are changing at alarming rates because of climate change and a wide variety of other anthropogenic stressors. These stressors have the potential to cause phase shifts to less productive ecosystems. A major challenge for ecologists is to identify ecosystem attributes that enhance resilience and can buffer systems from shifts to less desirable alternative states. In this study, we used the Northern Channel Islands, California, as a model kelp forest ecosystem that had been perturbed from the loss of an important sea star predator due to a sea star wasting disease. To determine the mechanisms that prevent phase shifts from productive kelp forests to less productive urchin barrens, we compared pre‐ and postdisease predator assemblages as predictors of purple urchin densities. We found that prior to the onset of the disease outbreak, the sunflower sea star exerted strong predation pressures and was able to suppress purple urchin populations effectively. After the disease outbreak, which functionally extirpated the sunflower star, we found that the ecosystem response—urchin and algal abundances—depended on the abundance and/or size of remaining predator species. Inside Marine Protected Areas (MPAs), the large numbers and sizes of other urchin predators suppressed purple urchin populations resulting in kelp and understory algal growth. Outside of the MPAs, where these alternative urchin predators are fished, less abundant, and smaller, urchin populations grew dramatically in the absence of sunflower stars resulting in less kelp at these locations. Our results demonstrate that protected trophic redundancy inside MPAs creates a net of stability that could limit kelp forest ecosystem phase shifts to less desirable, alternative states when perturbed. This highlights the importance of harboring diversity and managing predator guilds.

The evolution of respiratory systems in Theropoda and Paracrocodylomorpha, the end-Triassic extinction, and the role of Late Triassic atmospheric O2 and CO2

During the Late Triassic Period (235–201.3 Ma), Paracrocodylomorpha and Theropoda switched predatory roles, with the former filling the subsidiary predator niche and the latter filling the top predator niche at the end-Triassic extinction. Reasons for the transition in predator guilds remain unknown, but atmospheric conditions during this time, which involved high CO2 and low O2 concentration levels, may be associated with the event. Evidence of bird-like pneumatic post-crania, present in both groups as foramina and fossae, correlates with an avian-like respiratory system. This may have allowed organisms to cope with declining atmospheric O2 environments of the Late Triassic. This study estimated pO2 throughout the late Triassic using organic carbon isotope measurements from Newark-Hartford basin paleosols and examined the morphological change in skeletal remains of Theropoda, focusing on pneumatic bones, compared with Paracrocodylomorpha during the Late Triassic and across the Triassic-Jurassic boundary. With data compiled from the Paleobiology Database and published anatomical literature, the change of pneumaticity in taxa is quantified by a Pneumatic Index (PI), in which the number of pneumatized units is divided by the total number of bones examined. Patterns of pneumaticity are individually scored for the presence or absence of pneumatic bones. Morphological data are compared to corresponding femur length, estimated atmospheric O2 and CO2 level reconstructions, and an ancestral state reconstruction depicting how PI values change throughout various clades. Our results suggest that PI values in Theropoda and Paracrocodylomorpha correspond with the vacillating pO2 and pCO2 throughout the Late Triassic and into the Jurassic. High PI values are prevalent in advanced theropod taxa, while Paracrocodylomorpha PI values vary by clade with a generally negative trend throughout the Triassic. Ancestral state reconstruction analysis highlights the increasing PI values within Theropoda and clade dependent trends in Paracrocodylomorpha. This study is instrumental in reconstructing how Theropoda became evolutionarily successful and perhaps how and why the avian-like respiratory system originated.

Contrasting functional structure of saproxylic beetle assemblages associated to different microhabitats

Saproxylic beetles depend on diverse microhabitats that are exploited by different species assemblages. We focused on analysing the functional trait patterns and functional diversity components of two main assemblages that were collected with window traps (WTs) and hollow emergence traps (HETs) respectively, between three protected areas of the Iberian Peninsula. For that we measured phenological, physiological, morphological, and ecological traits. Results showed that the main microhabitats exploited by each assemblage (WT and HET) constrain most of the morphological traits and trophic guilds. In addition, relative elytra length and predator guild, together with adult activity period, responded to differences at the habitat level (among study areas). HET assemblages were less taxonomically diverse but more functionally diverse than those of WTs, enhancing the functional relevance of tree hollows. Additionally, niche filtering dominated WT assemblages, which were characterised by a narrower functional space and a higher redundancy. In contrast, in the HET assemblages the coexistence of functionally dissimilar species is driven by the niche heterogeneity. HET and WT assemblages differed in the functional space occupied by each within areas, but both assemblages reflected coincident patterns among areas that pointed to a reduction of functional space with management.

A multiscale assessment of Red-tailed Hawk reproductive success relative to urban density and habitat type

AbstractDespite the unique threats to wildlife in urban areas, many raptors have established successfully reproducing urban populations. To identify variations in raptor breeding ecology within an urban area, we compared metrics of Red-tailed Hawk reproductive attempts to landscape characteristics in Reno and Sparks, NV, USA during the 2015 and 2016 breeding seasons. We used the Apparent Nesting Success and logistic exposure methods to measure nesting success of the Red-tailed Hawks. We used generalized linear models to relate nesting success and fledge rate to habitat type, productivity to hatch date (Julian day) and hatch date to urban density. Nesting success was 86% and 83% for the respective years. Nesting success increased in grassland-agricultural and shrub habitats and decreased in riparian habitat within the urban landscape. Productivity was 2.23 and 2.03 per nest for the breeding seasons. Fledge rates were 72% and 77%, respectively, and decreased in riparian areas. Nestlings hatched earlier with increased urban density and earliest in suburban areas, following a negative quadratic curve. Nesting success and productivity for this population were high relative to others in North America. Productivity increased in habitats where ground prey was more accessible. We suggest that suburban areas, if not frequently disturbed, provide sufficient resources to sustain Red-tailed Hawks over extended periods. As urban expansion continues in arid environments globally, we stress that researchers monitor reproductive output across the urban predator guild to elucidate patterns in population dynamics and adaptation.

Predator type influences the frequency of functional responses to prey in marine habitats.

The functional response of a consumer to a gradient of resource density is a widespread and consistent framework used to quantify the importance of consumption to population dynamics and stability. Within benthic marine ecosystems, both crustaceans and fishes can provide strong top-down pressure on prey populations. Taxon-specific differences in biomechanics or habitat use, among other factors, may lead to variable functional response forms or parameter values (attack rate, handling time). Based on a review of 189 individual functional response fits, we find that these predator guilds differ in their frequency distribution of functional response types, with crustaceans exhibiting nearly double the proportion of sigmoidal, density-dependent functional responses (Holling type III) as predatory fishes. The implications of this finding for prey population stability are significant because type III responses allow prey persistence while type II responses are de-stabilizing and can lead to extinction. Comparing per capita predation rates across diverse taxa can provide integrative insights into predatory effects and the ability of predation to drive community structure.

Perspectives of traditional Himalayan communities on fostering coexistence with Himalayan wolf and snow leopard

AbstractThe Himalayan wolf Canis sp. and snow leopard Panthera uncia are found in the Nepalese Himalayas where conservation efforts target the latter but not the former. We conducted semistructured questionnaire surveys of 71 residents in upper Humla, upper Dolpa, and Kanchenjunga Conservation Area (KCA) during 2014–2016 to understand people's knowledge, perceptions, attitudes and interactions with these two carnivores. We fitted a cumulative link mixed model to predict Likert scale ordinal responses from a series of Generalized Linear Mixed Models. Overall, attitudes were more positive toward snow leopards than wolves. Livestock depredation was the main predictor of the general negative attitude toward wolves (Estimate = −1.30873; p = .029866) but there was no evidence for an effect for snow leopards (Estimate = −0.3640; p = .631446). Agropastoralists had more negative attitudes than respondents with other occupations toward both carnivores and men had more positive attitudes than women. Among our study areas, respondents in the community‐owned KCA had the most positive attitudes. Our findings illustrate the need to reduce human–carnivore conflict through a combined approach of education, mitigation, and economic cost‐sharing with respectful engagement of local communities. Specifically, to encourage more villagers to participate in livestock insurance schemes, they should be improved by including all large carnivores and adjusting compensation to the market value of a young replacement of the depredated livestock type. Carnivore conservation interventions should target the whole predator guild to achieve long‐term success and to protect the Himalayan ecosystem at large.

Hoverfly diversity (Diptera: Syrphidae) of Pyrenean oak woodlands in Central-Western Spain: a preliminary study with conservation outcomes

Hoverflies are frequently used as biodiversity indicators and are targets of ecological studies across Europe. How hoverfly diversity responds to ecological variables is essential for species and habitat conservation. The present study is a first attempt to assess the hoverfly diversity of deciduous woodlands of Pyrenean oak (Quercus pyrenaica) in La Vera (Central-Western Spain), a habitat in need of conservation and a region that is poorly known in terms of hoverflies. Hoverflies were sampled with hand net in a mature-woodland site, a young-woodland site, and two close-by grassland sites. A higher number of species and individuals was recorded in woodland sites than in grassland sites, with only two species exclusive to the grasslands and thus, suggesting that woodland sites might be acting as a hoverfly reservoir and source. The proportion of species with phytophagous and saprophagous larvae in woodland sites was higher than outside the woodlands, probably due to a higher availability of resources in woodland sites for phytophagous and saprophagous species. The mature woodland was found to have a higher number of species and individuals than the young woodland, possibly due to the presence of grassy clearings and rotting materials in the trees of the mature woodland. The highest number of species was found in the predatory guild (Syrphinae), and smaller-bodied species within this guild were found to be more frequent in grassland than in woodland sites; possible explanations for this result are discussed. Further investigation is required to confirm and expand the results and conclusions found in this initial study on the hoverfly community of the poorly studied Q. pyrenaica woodlands of Central-Western Spain.

Deep learning and taphonomy: high accuracy in the classification of cut marks made on fleshed and defleshed bones using convolutional neural networks

Accurate identification of bone surface modifications (BSM) is crucial for the taphonomic understanding of archaeological and paleontological sites. Critical interpretations of when humans started eating meat and animal fat or when they started using stone tools, or when they occupied new continents or interacted with predatory guilds impinge on accurate identifications of BSM. Until now, interpretations of Plio-Pleistocene BSM have been contentious because of the high uncertainty in discriminating among taphonomic agents. Recently, the use of machine learning algorithms has yielded high accuracy in the identification of BSM. A branch of machine learning methods based on imaging, computer vision (CV), has opened the door to a more objective and accurate method of BSM identification. The present work has selected two extremely similar types of BSM (cut marks made on fleshed an defleshed bones) to test the immense potential of artificial intelligence methods. This CV approach not only produced the highest accuracy in the classification of these types of BSM until present (95% on complete images of BSM and 88.89% of images of only internal mark features), but it also has enabled a method for determining which inconspicuous microscopic features determine successful BSM discrimination. The potential of this method in other areas of taphonomy and paleobiology is enormous.

Spatio‐temporal factors impacting encounter occurrences between leopards and other large African predators

AbstractEncounters between individuals can have implications for a range of processes, including disease transmission, information transfer and competition. For large carnivores, difficulties in directly observing individuals and historical hardware limitations of GPS collars mean that relatively little is known of the spatio‐temporal factors contributing to encounters. The African large predator guild represents one of the few remaining functionally intact guilds of large carnivores on the globe and so represents a unique study system for understanding competitor interactions. We explored the drivers of male leopard (Panthera pardus) encounters with lions (Panthera leo), African wild dogs (Lycaon pictus) and cheetahs (Acinonyx jubatus) in the context of habitat characteristics and temporal activity overlaps. Using high‐resolution (five minute GPS fixes) data from 48 large African carnivores from 2012 to 2018, we quantified encounter occurrences between male leopards and other guild species and related these to habitat type (open vs closed), activity overlaps and moonlight levels. Leopards met wild dogs 4.56 ± 1.15 (standard error), lions 3.11 ± 0.56 and cheetahs 2.27 ± 0.73 times per month. All species instigated encounters, but leopard instigated encounters with dominant competitors appeared to reflect imperfect information on risk, primarily occurring within habitats with limited visibility. Moreover, encounters peaked during periods of high temporal overlap, suggesting that, although previous research indicates temporal activity patterns may not be driven by predator avoidance, temporal overlap has implications for competitor dynamics. Our results show how habitat characteristics and niche overlaps contribute to encounters between competitors and provide an example of how niche shifts within competitor assemblages can impact competition between species.

Trophic structure of the macrofauna associated to deep-vents of the southern Gulf of California: Pescadero Basin and Pescadero Transform Fault.

Newly discovered hydrothermal systems in the Pescadero Basin (PB) and the neighboring Pescadero Transform Fault (PTF) at the mouth of the Gulf of California disclosed a diverse macrofauna assemblage. The trophic structure of both ecosystems was assessed using carbon (δ13C), nitrogen (δ15N), and sulfur (δ34S) stable isotopes. The δ13C ranged from -40.8 to -12.1‰, revealing diverse carbon sources and its assimilation via Calvin-Benson-Bassham and the reductive tricarboxylic acid cycles. The δ15N values were between -12.5 and 18.3‰, corresponding to primary and secondary consumers. The δ34S values fluctuated from -36.2 to 15.1‰, indicating the sulfide assimilation of biogenic, magmatic, and photosynthetic sources. In PB high-temperature vents, primary consumers including symbiont-bearing, bacterivores and filter-feeders predominated. The secondary consumers within the scavengers/detritivores and predator guilds were scarce. The siboglinid Oasisia aff alvinae dominated the macrofauna assemblage at PB, but rather than playing a trophic role, it provides a substrate to vent dwellers. In PTF low-temperature vents, only symbiont-bearing primary consumers were analyzed, displaying the lowest δ34S values. This assemblage was dominated by the coexisting siboglinids Lamellibrachia barhami and Escarpia spicata. δ34S values allowed to distinguish between PB and PTF vent communities, to exclude the presence of methanotrophic organisms, and the detection of photosynthetic organic matter input.

Interacting Effects of Eyespot Number and Ultraviolet Reflectivity on Predation Risk in Bicyclus anynana (Lepidoptera: Nymphalidae).

Small marginal eyespots on lepidopteran wings are conspicuous elements that attract a predator’s attention to deflect attacks away from the body, but the role of ultraviolet (UV) reflectivity at the center of these patterns and variation in eyespot number in altering the function of eyespots remains unclear. Here, we performed a field-based predation experiment with artificial prey items based on the appearance of squinting bush brown butterflies Bicyclus anynana (Butler, 1879). We tested how two visual properties of the wing pattern affect predation risk: i) the number of eyespots on the ventral forewing surface—two or four; and ii) the UV reflectivity of eyespot centers—normal (where the UV reflectivity of the centers contrasts strongly with that of the darker surrounding ring) or blocked (where this contrast is reduced). In total, 807 prey items were deployed at two sites. We found a significant interaction between the number of ventral forewing eyespots and UV reflectivity in the eyespot centers: in items with fewer eyespots, blocking UV resulted in increased predation risk whereas in items with more eyespots, blocking UV resulted in decreased predation risk. If higher predation of paper models can be equated with higher levels of wing margin/eyespot conspicuity, these results demonstrate that UV reflectivity is an important factor in making eyespots more conspicuous to predators and suggest that the fitness of particular butterfly eyespot number variants may depend on the presence or absence of UV in their centers and on the ability of local predator guilds to detect UV.

Do Parents Synchronise Nest Visits as an Antipredator Adaptation in Birds of New Zealand and Tasmania?

Birds with altricial offspring need to feed them regularly, but each feeding visit risks drawing attention to the nest and revealing its location to potential predators. Synchronisation of visits by both parents has been suggested as a behavioural adaptation to reduce the risk of nest predation. Under this hypothesis, higher risk of nest predation favours greater synchrony of parental feeding visits. We investigated this prediction over three timescales using nestling provisioning data from 24 passerine species in Tasmania and New Zealand. We estimated the extent to which parents actively synchronised their visits to the nest by comparing observed patterns of synchrony with those expected to occur at random. We found that in general, species did not synchronise visits more often than expected by chance. Species varied in the tendency to synchronise visits, but this variation was not explained by likely predation pressure in the distant evolutionary past: New Zealand endemic species, which evolved in the absence of mammalian nest predators, synchronised their visits as often as species which evolved with more diverse predatory guilds. Nest predation risk has increased over time in New Zealand due to introduced predators, but synchrony in visits also was not explained by manipulated predation risk: visit synchrony was equivalent between a predator-removal site and a site where predators remained. However, within one New Zealand species, visit synchrony was higher for mainland populations, which have been exposed to predatory mammals for c.800 years, than for a population on an offshore island to which predatory mammals were never introduced. We conclude that breeding birds may have some capacity to adapt the synchrony with which they provision over short evolutionary timescales. However, the lack of synchrony in most species suggests that either asynchrony provides benefits that outweigh the greater risk of predation, or synchrony incurs costs not compensated by reduced predation.

Fluorescence in Fireflies (Coleoptera: Lampyridae): Using Sentinel Prey to Investigate a Possible Aposematic Signal

While fireflies are most renowned for their bioluminescent signals, several species also have been shown to possess UV and blue-induced fluorescence. In a field study, we used a sentinel prey approach to investigate whether this trait might serve as an aposematic function in chemically defended fireflies. We also examined and provide the first detailed description of green and red patterns of blue light-induced fluorescence in the adults and larvae of Ellychnia corrusca (L.) (Coleoptera: Lampyridae). We placed artificial prey models with and without fluorescent markings in a forested area of Belmont, Massachusetts, USA, where they were exposed to natural predators. Clay models were styled to resemble Photinus fireflies, the most common firefly genus in this area, and a close relative of Ellychnia. The field study was conducted from Oct through May in Belmont, Massachusetts; this is the period when adults of the diurnal non-luminescent firefly E. corrusca are overwintering on trees. We observed considerable seasonal variation in attack rates, and marks on the clay models indicated they were attacked by avian, mammal, and arthropod predators. However, no difference was seen between fluorescent and non-fluorescent models in predator attack rates. This suggests that fireflies' fluorescent markings do not serve as an aposematic signal, at least for the predator guild active in New England woodlands.