Reduce Predation Risk Research Articles

Ecological drivers of the high predation of sea turtle hatchlings during emergence

Synchronized emergence of offspring may represent an adaptive strategy to reduce predation risk. This strategy swamps the short-term capacity of predators to consume prey before offspring disperse, inducing a dilution effect, thus improving an individual’s chance of survival. In the case of sea turtles, this occurs during emergence and mass migration to the sea, to avoid potential predators on the beach. In this study, we evaluated the effect of group size on predation rates of loggerhead turtle Caretta caretta hatchlings during the crawl to the sea on Boa Vista Island, Cabo Verde. Our results show that synchronous emergence reduced rates of predation by tufted ghost crabs Ocypode cursor. The mean estimated predation rate overall was 50.3%. Predation was highest (~75%) in the smallest group sizes and decreased to ~25% in larger groups, due to the lower probability of an individual being attacked by a ghost crab. Our observations also indicate significantly higher predation rates at night (55%) than during the day (22%). No relationship between predation rates and the distance between the nest and the surf zone of the sea was identified; however, this is likely due to the behaviour of ghost crabs, i.e. waiting close to the tide line for hatchlings during the night. Our results provide important information for the management and conservation of endangered sea turtle populations in areas with high densities of predatory ghost crabs. Specifically, to reduce predation rates, we recommend that hatchlings are released in large groups at twilight hours and in areas of low ghost crab densities.

Crepuscular hunting of swiftlets (Family: Apodidae) by Besra (Family: Accipitridae) in the urban areas of the Andaman Islands, India

We report the crepuscular hunting behavior by the Besra Accipiter virgatus, on the Glossy Swiftlets Collocalia esculenta affinis and the Edible-nest Swiftlets Aerodramus fuciphagus inexpectatus in urban areas the Andaman & Nicobar Islands. Unlike other raptors in the islands, the Besra hunts at twilight often in the absence of moonlight or/and artificial light. Glossy and Edible-nest Swiftlets have been ranched in human habitations and their nests harvested for livelihood support of local communities under an ex situ conservation program. Using the focal animal sampling method, we recorded the hunting behavior of the Besra (the predator) on the swiftlets (the prey) for 40h (120 min/day for 20 days) at the ex situ swiftlet colony established in a house in the Middle Andamans. The Besra made 84 hunting attempts, with the highest success rate (15.4%) between 17.00–18.00 h. The catch rate was a mean of 4±11 (SD) per day. The maximum time that was used for attempt to kill the prey was two hours. Depredation of the Edible-nest Swiftlet by the Besra could affect ex situ conservation efforts, which can also lead to economic losses and retaliation against the raptor. Restricting perch sites for the raptor around ranching houses might reduce predation risks for the swiftlets.

Insect alarm pheromones in response to predators: Ecological trade-offs and molecular mechanisms

Insect alarm pheromones are chemical substances that are synthesized and released in response to predators to reduce predation risk. Alarm pheromones can also be perceived by predators, who take advantage of alarm cues to locate prey. While selection favors evolution of alarm pheromone signals that are not easily detectable by predators, predator evolution selects for better prey detection ability. Here, we review the diversity of alarm signals, and consider the behavioral and ecological conditions under which they have evolved. We show that components of alarm pheromones are similar across many insects, although aphids exhibit different behavioral responses to alarm cues compared to social insects. The effects of alarm pheromones on prey behavior depend on factors such as the concentration of pheromones and the density of conspecifics. We also discuss the molecular mechanisms of alarm pheromone perception underlying the evolutionary arms race between predators and prey, and the function of olfactory proteins and receptors in particular. Our review provides a novel synthesis of the diversity and function of insect alarm pheromones, while suggesting avenues that might better allow researchers to exploit population-level responses to alarm signaling for the sustainable management of pests and vector-borne pathogens.

Sex‐specific effects of predation risk on parental care in a sexually dichromatic Neotropical songbird

Predation risk affects a broad range of bird behaviours, especially parental care. The adaptive behavioural changes presented by both parents, however, may differ according to different levels of predation risk suffered by each sex. This is especially prominent in sexually dichromatic species, where one of the sexes is more visually conspicuous and hence vulnerable to increased nest predation risk during nest visits. Here, we experimentally investigated how predation risk affects the parental behaviour of a sexually dichromatic Neotropical passerine, the blue‐black grassquit Volatinia jacarina. We used playbacks of known predators and non‐predatorial control sympatric species near nesting pairs in the field. Results show that grassquits modify their behaviour according to predation risk and that this behavioural response is sex‐dependent. Males decrease their nest visit times, become more discreet when moving towards the nest, and stop performing sexual displays after leaving the nest. In contrast, females tend to decrease latency to visit the nest and increase the duration of brooding bouts. These different sex responses reduce nest visual and acoustic detectability, since conspicuous males are readily spotted on nests and cryptic females camouflage nestlings and suppress begging calls. Although these behavioural changes might reduce predation risk, there might be a cost of reduced food load to nestlings and increased brood starvation risk. These changes in nesting activities illustrate the behavioural adaptability of passerines to ensure offspring survival in tropical high predation risk environments.

Ontogenetic shifts in social aggregation and habitat use in a temperate reef fish

AbstractCover, both from physical structure or association with social groups, can reduce predation risk and increase foraging, leading to enhanced growth and survival, and is therefore a critical aspect of the niche for many organisms. However, the need for cover, or the need for a specific type of cover, may change as an individual grows in size, leading to niche shifts throughout development to meet these changing needs. In this study, we examine ontogenetic shifts in cover use by wild populations of a temperate reef fish, the southern hulafish, Trachinops caudimaculatus, a small, abundant planktivorous social aggregator found on temperate reefs in southern Australia. Through repeated in situ surveys, we found clear evidence of ontogenetic shifts in both microhabitat use and aggregation patterns by T. caudimaculatus juveniles in the first three months on the reef. The microhabitat associations of juvenile T. caudimaculatus became more similar to those of adult conspecifics over the study period, and over the same time frame, juveniles increasingly aggregated with adult shoals. Our findings also suggest that trade‐offs between structural and social cover are context‐dependent, with juveniles relying on structural cover longer when adult conspecific density (and thus intra‐specific competition) and/or habitat complexity (and thus the availability of shelter) is high. These findings provide rare and important observations into the complex interplay of social aggregations, habitat use, and ontogeny in wild fish populations.

On nest-site copying, owner aggression, and mimicry: the adaptive significance of interspecific information use in a landscape of fear

There is increasing evidence for species using information from heterospecifics to assess predation risk or habitat quality. Notably, a series of influential studies, using geometric symbols added to nest boxes, has shown that migratory flycatchers copy tits’ apparent nest-site preferences and settle in nest boxes bearing the same symbol as tits’ nest boxes. This “Selective Interspecific Information Use” hypothesis was recently challenged by the “Owner Aggression” hypothesis, stating that nest occupancy patterns are instead driven by tits aggressively excluding flycatchers from particular empty boxes to use as potential re-nesting sites after nest predation. Here, I propose the “Adaptive Interspecific Information Use” hypothesis, which outlines the predicted fitness benefits of nest-site copying or rejecting, and, importantly, provides an explanation for inconsistent experimental results to date. Indeed, neither previous hypotheses satisfactorily explains why flycatchers switch from copying to avoiding tits’ preferences, when tits’ clutch sizes are small or tits are at the laying stage. Adding to the recent debate, I show how predictable changes in nest predators’ search image and tits’ anti-predator behaviour may explain this variation. Indeed, incubating tit species aggressively defend their nest against nest predators, including by emitting snake-like vocalisations, which may generally deter predators from boxes bearing a tit nest symbol. By contrast, the undefended tit nests—which occur during laying before incubation starts, or potentially in individuals with small clutches—are easy prey that predators may specifically target. If predators cue on tit nests’ symbol, I therefore predict that, to reduce predation risk throughout the season, flycatchers may switch from avoiding the symbol of undefended tit nests to preferring the symbol of tits incubating large clutches. I propose experiments to test these predictions. Overall, considering nest-site copying in the landscape of fear framework, rather than invalidating the Selective Interspecific Information Use hypothesis, may be key to understand its evolution.

Plains zebras bring evidence that dilution and detection effects may not always matter behaviorally and demographically

AbstractGroup living is assumed to benefit prey by reducing predation risk due to dilution and detection effects. This increased safety could be exchanged against a reduced individual vigilance leading to increased foraging and fitness until costs of intra‐group competition offset this benefit. However, very few studies have been able to directly test the relationship between individual fitness and group size in non‐cooperative breeding species. Therefore, evidence that dilution and detection effects do indeed translate into increased fitness under predation risk remains mostly theoretical. Here, we aimed at empirically testing whether group size influences beneficial and costly behaviors, and ultimately the survival of individuals, in a prey species facing heavy predation pressure. We focused on plains zebra Equus quagga of Hwange National Park in Zimbabwe, a high lion density area. We collected behavioral data (i.e., individual vigilance and foraging, collective vigilance, and agonistic interactions) that we used as proxies to investigate the costs and benefits of grouping in this species. We then fitted multistate capture‐mark‐recapture and Cox proportional‐hazards models to estimate apparent survival of adults and young zebras, respectively, and assess whether a demographic signal of group size could be found. Our results show that collective vigilance increases with group size, a prerequisite of the detection effect, but individual vigilance does not consistently decrease with group size, which suggests that there is no group size effect on individual vigilance. Agonistic interactions were rare. These results suggest that there are no foraging costs of grouping here, and even some benefits such as a better collective vigilance. However, any benefits of being in larger groups did not translate into increased survival, as we found no effect of group size on the apparent survival of individuals. Since dilution and detection effects do not matter behaviorally and demographically in these plains zebras living under high predation risk, these results challenge our understanding of how predation shapes animal sociality: fitness benefits of dilution or detection should not be assumed.

Habitat structure and association with ungulates drive habitat selection and grouping behaviour of lesser rhea (Rhea pennatasubsp.pennata)

AbstractSocial prey species respond to predation risk by modifying habitat selection and grouping behaviour. These responses may depend on both actual predation risk (predator probability of occurrence) and/or on perceived predation risk associated with habitat structure. Other factors like food availability and co‐occurrence with other species may also affect habitat selection and group formation. We analyse habitat selection and grouping behaviour (group size and cohesion) of lesser rhea (Rhea pennatasubsp.pennata), a ratite endemic of South America inhabiting steppe shrublands and grasslands, in relation to actual (puma probability of occurrence) and perceived (habitat structure: openness, visibility) predation risk, co‐occurrence with other herbivore species and forage availability in the Chilean Patagonia. We used data from 9 sampling seasons in 5 years. Results show that habitat selection, group size and cohesion in lesser rhea were mainly driven by variables associated with perceived predation risk and by co‐occurrence with other herbivores both during breeding and non–breeding season. As expected, lesser rhea preferred open habitats (vegas and grasslands) that allow a behaviour of ‘watch and run’ to avoid predation and formed larger groups in them. Moreover, lesser rhea positively selected year‐round habitats where livestock occur, forming large groups during non–breeding season there. Group size and co‐occurrence with other herbivores significantly decreased group cohesion, suggesting a reduction of perceived predation risk. Therefore, lesser rhea seems to take advantage of forming mixed interspecific groups to reduce predation risk. These results suggest that lesser rhea habitat selection and grouping behaviour are preferentially driven by factors related to perceived predation risk than by actual predator occurrence or food availability.

Tidal–diel patterns of movement, activity and habitat use by juvenile mangrove whiprays using towed-float GPS telemetry

Stingrays are a diverse and widespread group of elasmobranchs. Despite their ecological and economical importance, many aspects of stingray ecology remain poorly understood. Few studies have examined fine-scale movements of juvenile stingrays within nursery areas. This study aimed to examine diel movement patterns in juvenile mangrove whiprays (Urogymnus granulatus) by using towed-float GPS telemetry within a reef flat habitat of the Great Barrier Reef. Juvenile mangrove whiprays travelled distances from 394 to 2189m, moving at a rate (mean±s.e.) of 3.97m min–1±2.5 during tracking periods ranging from 1.35 to 9h. Movements of juvenile mangrove whiprays were influenced by tidal height and diel period. Individuals chose more direct paths during outgoing and incoming tides and their activity space was significantly larger during the day than at night-time. Individuals showed preference for mangrove areas during high tides, which was likely to reduce predation risk. Our findings have established the use of the towed-float GPS telemetry as an effective tool to assess short-term movement patterns and habitat use of juvenile stingrays, as well as highlighted how juvenile mangrove whiprays use reef-flat environments.

Fossoriality in a risky landscape: badger sett use varies with perceived wolf risk

AbstractMany medium‐sized carnivores are fossorial and use burrow systems to reduce predation risk or avoid predators. But fossorial species cannot stay safely underground forever, and they must also risk emerging overground, to forage and find mates. To make this trade‐off effectively and maximize their own fitness, it is imperative they assess how predation risk varies in space and time, and adapt their denning behaviour accordingly. We used European badger (Meles meles) burrows (setts) in Białowieża Forest, Poland as a model for investigating how the denning behaviour of a fossorial mesocarnivore varies across gradients of landscape scale perceived risk imposed by wolves (Canis lupus) and humans, defined as wolf space use and distance to settlements, respectively. We monitored seventeen setts with varying levels of perceived human and wolf risk with camera traps for two months to study three denning behaviours: frequency of badger sett use, frequency of badger sett sharing with other mesocarnivore species and badger emergence time. Frequency of sett use varied relative to perceived wolf but not human risk. Setts in the highest risk areas were used ca. 60% less often than those in the lowest perceived risk areas, and setts with juveniles were only present in areas of lower perceived risk. Food availability, quantified as earthworm abundance in an area of 2.1 km2 around setts, did not affect the frequency setts were used. Emergence time and frequency of sett sharing with other mesocarnivores, which have been proposed to be anti‐predator strategies, did not vary with either perceived risk factor. These results show fossorial species can adapt their use of burrows to the prevailing risk landscape and suggest burrows deserve more attention in studies on the ecological impacts of apex predators.

Environmental gradients influence biogeographic patterns of nonconsumptive predator effects on oysters

AbstractWhen prey alter behavioral or morphological traits to reduce predation risk, they often incur fitness costs through reduced growth and reproduction as well as increased mortality that are known as nonconsumptive effects (NCEs). Environmental context and trophic structure can individually alter the strength of NCEs, yet the interactive influence of these contexts in natural settings is less understood. At six sites across 1000 km of the Southeastern Atlantic Bight (SAB), we constructed oyster reefs with one, two, or three trophic levels and evaluated the traits of focal juvenile oysters exposed to predation risk cues. We monitored environmental variables (water flow velocity, microalgal resources, and oyster larval recruitment) that may have altered how oysters respond to risk, and we also assessed the cost of trait changes to oyster mortality and growth when they were protected from direct predatory loss. Regardless of trophic structure, we found that oyster shell strength and natural oyster recruitment peaked at the center of the region. This high recruitment negated the potential for NCEs by smothering and killing the focal oysters. Also independent of trophic structure, focal oysters grew the most at the northernmost site. In contrast to, and perhaps because of, these strong environmental effects, the oyster traits of condition index and larval recruitment were only suppressed by the trophic treatment with a full complement of risk cues from intermediate and top predators at just the southernmost site. But at this same site, statistically significant NCEs on oyster growth and mortality were not detected. More strikingly, our study demonstrated environmental gradients that differentially influence oysters throughout the SAB. In particular, the results of our trophic manipulation experiment across these gradients suggest that in the absence of predation, environmental differences among sites may overwhelm the influence of NCEs on prey traits and population dynamics.

Solitary versus group living lifestyles, social group composition and cooperation in otters

Increased reproduction success, enhanced foraging and reduced predation risk are usually regarded as major factors favouring the evolution of social behaviour. Here we formulate a series of hypotheses relating sexual, ecological and behavioural factors to evaluate their explanatory value for 13 extant otter species, estimating the extent to which each factor contributes to the sociality of each species. We also compare individual behaviours within some of the species. Four otter species are obligatory social; four are obligatory solitary; five present both types of social organization. Social organizations of otter species are not related to their phylogenetic relationships. However, many otter species exhibit intra-species patterns of flexible social lifestyles. Both solitary and social otters adjust their social patterns in response chiefly to food availability, but also to habitat features and competition.Group living is more common when intraspecific competition is reduced or trophic resources replenish rapidly. Under these circumstances, group members often forage individually. When otters forage individually, they often switch prey type when they compete with other conspecifics. Social structures of otters fall into seven types: (1) family groups; (2) extended family groups, often with an alpha dominant pair; (3) highly social groups with helpers; (4) collective hunting groups; (5) solitary lifestyle; (6) unstable mixed-sex groups; and (7) single-sex bachelor groups. When an individual of a species with variable sociality adopts one type of sociality, this may be only temporary. Variations in social life are actually based on a series of events that induce individuals to make decisions taking ecological factors into account.Although ontogenetic factors can influence delayed dispersal of otters, social factors rather than ecological factors could play an important role in the formation of groups, and cohesiveness and kinship appear to be secondary effects of reduced dispersal more than primary causes for living in a group. Appropriate adjustment of group behaviour reduces the cost of sociality because individuals avoid social interactions when benefits are low but gather together when group living provides real advantages. Although any one model is unlikely to explicate all facets of sociality, evolution towards a social group results mainly from interactions within a family.

Rapid evolution and plasticity of genitalia.

Genital morphology exhibits tremendous variation and is intimately linked with fitness. Sexual selection, nonmating natural selection and neutral forces have been explored as potential drivers of genital divergence. Though less explored, genitalia may also be plastic in response to the developmental environment. In poeciliid fishes, the length of the male intromittent organ, the gonopodium, may be driven by sexual selection if longer gonopodia attract females or aid in forced copulation attempts or by nonmating natural selection if shorter gonopodia allow predator evasion. The rearing environment may also affect gonopodium development. Using an experimental introduction of Trinidadian guppies into four replicate streams with reduced predation risk, we tested whether this new environment caused the evolution of genitalia. We measured gonopodium length after rearing the source and introduced populations for two generations in the laboratory to remove maternal and other environmental effects. We split full-sibling brothers into different rearing treatments to additionally test for developmental plasticity of gonopodia in response to predator cues and food levels as well as the evolution of plasticity. The introduced populations had shorter gonopodia after accounting for body size, demonstrating rapid genital evolution in 2-3years (8-12 generations). Brothers reared on low food levels had longer gonopodia relative to body size than those on high food, reflecting maintenance of gonopodium length despite a reduction in body size. In contrast, gonopodium length was not significantly different in response to the presence or absence of predator cues. Because the plastic response to low food was maintained between the source and introduced populations, there was no evidence that plasticity evolved. This study demonstrates the importance of both evolution and developmental plasticity in explaining genital variation.

Red Fox Use of Landscapes with Nesting Shorebirds

ABSTRACTPredation of nests and young is one of the limiting factors in the conservation of birds; understanding environmental covariates of predator distribution can assist with decisions regarding the best management strategies to reduce predation risk. The habitat of beach‐nesting birds is often reshaped by storms in ways that may affect nest predation, such as by flattening vegetated dunes where mammals hunt, but human management of beaches tries to prevent the effects of storms on the landscape with unknown implications for predator distributions. Moreover, human development may affect predator distributions by subsidizing food and shelter. To determine the relationship between predator occupancy and landscape features in beach‐nesting bird habitat, we repeated mammalian predator track surveys 8 times/year at 90 plots in southern New Jersey, USA, from 2015–2017. We used dynamic occupancy models to estimate the probability of use by red foxes (Vulpes vulpes) and to document changes in habitat use as related to landcover types over the avian breeding season within years. We had 373 red fox detections with years pooled. Detection probability for red foxes varied by year, and probability of use decreased as the distance to the nearest primary dune increased. We found no evidence that red fox habitat use depended on distance to human development. Our results suggest that conserving nesting habitat that includes open areas (i.e., storm overwash [whereby vegetation is scoured by tidal flooding]) may reduce predation risk because beach‐nesting birds would not be forced into nesting close to dunes, which are typically used for hunting by red foxes. © 2020 The Wildlife Society.

Giraffe diurnal recumbent behavior and habitat utilization in Katavi National Park, Tanzania

AbstractResting behaviors play an important role in animals’ daily activities by minimizing energy consumption. Although this may be equally important to other behavioral states for sustaining life, it has not been well studied in the giraffe (Giraffa camelopardalis). This study characterized the bout duration, frequency, and age–sex class differences in diurnal recumbent behavior of free‐ranging giraffe. Additionally, it is currently unknown whether giraffe utilize shady or safe areas for diurnal recumbency, as many other animals do. Therefore, we also investigated this in the present study. Data were collected in Katavi National Park, Tanzania, during four time periods. The duration of recumbency bouts was calculated from 170 episodes, and the frequency of recumbency was determined by following 24 individuals for more than 10 h each. Habitat type was categorized into wooded grassland or miombo woodland, and habitat preference was analyzed based on 173.6 h of observations. We found no significant difference in the duration of recumbency bouts among the four age‐classes and between sexes in adults. On the other hand, calves (n = 2) rested more frequently than did other age‐groups, possibly due to differences in predation risk or activity budgets. Adult males had a higher frequency of recumbency compared to adult females, possibly because pregnant/nursing females were hindered in adopting this posture. We also found that giraffe primarily utilized the miombo woodland for daytime recumbency, likely because the high tree density reduces heat stress, and its seclusion from the river reduces predation risk.

Shifts in foraging behaviour of heterospecific flocking birds in a lowland Malaysian rainforest

Mixed-species flocks (MSFs) serve important roles in bird communities, especially in tropical forests. Although structure of mixed-species bird flocks and its benefits has been intensively studied globally, the foraging plasticity of a species when joining MSFs has rarely been evaluated. The present study examines foraging strategies of the Rufous-crowned Babbler (Malacopteron magnum), Chestnut-winged Babbler (Cyanoderma erythropterum) and Black-naped Monarch (Hypothymis azurea) when participating in MSFs in the Krau Wildlife Reserve, central Peninsular Malaysia. These species exhibit active foraging shifts in utilisation of vertical strata, foraging substrate, attack manoeuvres and foliage density, when foraging in MSFs, compared to when foraging outside MSFs. While the Rufous-crowned Babbler and Chestnut-winged Babbler commonly used gleaning and stretching (to completely extend the legs or neck to reach the food items) manoeuvres when foraging outside MSFs, respectively, they adopted probing manoeuvre and frequently used higher strata upon joining MSFs. The Chestnut-winged Babbler tended to forage on the underside of leaves and the Black-naped Monarch frequently utilised branches when joining MSFs, while they exclusively used aerial leaf litter and live green leaves, respectively, when foraging with conspecifics. The monarch also adopted the hovering manoeuvre and frequently foraged within denser foliage cover when joining MSFs. This study demonstrated that flock members exhibits foraging plasticity either through an expansion or active shift in foraging niches when participating in MSFs, thus suggesting the occurrence of possible foraging improvement and/or reductions in predation risk.

Risk of predation on offspring reduces parental provisioning, but not flight performance or survival across early life stages

Abstract Developmental responses can help young animals reduce predation risk but can also yield costs to performance and survival in subsequent life stages with major implications for lifetime fitness. Compensatory mechanisms may evolve to offset such costs, but evidence from natural systems is largely lacking. In songbirds, increased nest predation risk should favour reduced provisioning, but also young that fledge (leave their nest) at an earlier age. Both responses can result in fledglings with shorter wings, reduced mobility and decreased survival. Young may compensate for shorter wings developmentally by reallocating resources towards feather development or behaviourally by adjusting flight kinematics or habitat use. However, underfed young may lack the capacity to express these phenotypes due to insufficient resources or an inability to adjust allocation of resources. Using predation risk experiments and 29 years of observational field data, we test whether increased nest predation risk reduces flight performance and survival during the fledgling stage and explore potential mechanisms that might underlie these effects. We show that young from high‐risk nests did not leave the nest earlier on average, but wing growth was slower likely due to observed reductions in parental feeding rates. Wings were shorter in high‐risk nests when fledglings left the nest early. Yet, fledglings from high‐risk nests showed improved flight performance for a given wing length such that flight performance at fledging did not differ between young from high‐risk and low‐risk nests. Young from high‐risk nests may have offset the costs of shorter wings on flight performance by accelerating the emergence of flight feathers from their sheaths to reduce wing porosity, though evidence for this mechanism was mixed. Fledglings from high‐risk nests also selected habitat with denser woody vegetation compared with young from low‐risk nests. Together, these developmental and behavioural responses seem to mitigate the expected effects of increased nest predation risk on fledgling survival. Ultimately, our results show that offspring predation risk can affect parental provisioning and offspring morphology without major implications for performance and survival in subsequent life stages. A free Plain Language Summary can be found within the Supporting Information of this article.

Benthic habitat is an integral part of freshwater Mysis ecology.

Diel vertical migration (DVM) is common in aquatic organisms. The trade‐off between reduced predation risk in deeper, darker waters during the day and increased foraging opportunities closer to the surface at night is a leading hypothesis for DVM behaviour.Diel vertical migration behaviour has dominated research and assessment frameworks for Mysis, an omnivorous mid‐trophic level macroinvertebrate that exhibits strong DVM between benthic and pelagic habitats and plays key roles in many deep lake ecosystems. However, some historical literature and more recent evidence indicate that mysids also remain on the bottom at night, counter to expectations of DVM.We surveyed the freshwater Mysis literature using Web of Science (WoS; 1945–2019) to quantify the frequency of studies on demographics, diets, and feeding experiments that considered, assessed, or included Mysis that did not migrate vertically but remained in benthic habitats. We supplemented our WoS survey with literature searches for relevant papers published prior to 1945, journal articles and theses not listed in WoS, and additional references known to the authors but missing from WoS (e.g. only 47% of the papers used to evaluate in situ diets were identified by WoS).Results from the survey suggest that relatively little attention has been paid to the benthic components of Mysis ecology. Moreover, the literature suggests that reliance on Mysis sampling protocols using pelagic gear at night provides an incomplete picture of Mysis populations and their role in ecosystem structure and function.We summarise current knowledge of Mysis DVM and provide an expanded framework that more fully considers the role of benthic habitat. Acknowledging benthic habitat as an integral part of Mysis ecology will enable research to better understand the role of Mysis in food web processes.

Patterns of activity rhythms of invasive coypus Myocastor coypus inferred through camera-trapping.

Studies on activity rhythms are pivotal for the management of invasive alien species, as they provide basic insights into species basic ecology and may increase the success of control programs. The coypu Myocastor coypus, introduced from South America for fur farms, has become one of the most invasive rodents in Europe. Introduced coypus may affect crop productions, as well as natural vegetation and the breeding success of wading birds. In this study, we examined activity data collected through intensive camera-trapping in three Italian areas, including two natural areas in Northern and Central Italy, and a suburban area in Central Italy. Coypus were mostly diurnal in areas characterised by low predator pressure and, at night, they are mostly active in bright moonlight. Conversely, where predators, human pressure or numerical control programmes are present, coypus remarkably shift their behaviour towards crepuscular and night hours. In these last areas, nocturnal activity increased as moonlight decreased, possibly to reduce predation risk or encounters with humans. Where winter temperature are low, diurnal habits may have developed as a physiological adaptation and a strategy to preserve energy, potentially achieving a cost/effective thermal balance.Electronic supplementary materialThe online version of this article (10.1007/s42991-020-00052-8) contains supplementary material, which is available to authorized users.

Rodents' responses to manipulated plant litter and seed densities: implications for restoration.

Rodent populations in arid grasslands do not always track seed production, possibly due to high levels of plant litter. When natural disturbances are suppressed, litter accumulates becoming physically complex, causing rodents to harvest fewer seeds per equivalent time foraging. It also alters security from predation. Restoring natural disturbances may be an important element in conserving rodent communities. The aim of this study was to assess the influence of two levels of plant litter cover and seed densities on nocturnal rodent population characteristics in a semiarid grassland. Specifically, I hypothesized that kangaroo rats, pocket mice, grasshopper mice, and total rodents would be higher in the sparse plant litter treatment than dense litter, whereas deer mice would be lower in sparse plots. I further hypothesized that kangaroo rats and deer mice would be higher in the seed augmented treatment compared to the unseeded treatment. A prescribed fire removed litter in four of eight plots prior to sowing native seeds 1 year postfire into two burned and two unburned plots. Rodents were live-trapped during spring and fall 1 year. Sparse litter treatment had higher total rodent abundance, biomass, and frequency of offspring compared to dense plots indicating use of stored seeds. Banner-tailed kangaroo rats had higher abundance, implying reduced predation risk. Pocket mice body mass was greater in dense plots. After winter, seeded plots had higher kangaroo rat body mass and grasshopper mice abundance than unseeded, reflecting the use of stored seeds. These short term results demonstrate litter’s physical complexity may be equivalent to seed pulses on the responses of nocturnal rodents. Managers might positively influence grassland rodents by providing a mosaic of varying levels of plant litter.