Antipredator Behavior Research Articles

Blessing the rains down in Africa: spatiotemporal behaviour of the crested porcupine <em>Hystrix cristata</em> (Mammalia: Rodentia) in the rainy and dry seasons, in the African savannah

The assessment of habitat selection and temporal patterns of activity rhythms is paramount for wildlife conservation. Studies on behavioural ecology of wild mammals are particularly challenging in tropical areas, mostly when involving rare or elusive species. Despite being a common species in Italy, the crested porcupine Hystrix cristata is threatened of extinction throughout most of its sub-Saharan range. All available information on the ecology of this species has been collected in Italy, whereas no data is present in the scientific literature on spatiotemporal behaviour of this large rodent in Africa. In this work, we attempted to determine habitat selection and temporal patterns of activity rhythms of the crested porcupine in northern Benin and neighbouring countries, through intensive camera-trapping. We collected a total of 146 records of crested porcupine, 91 in the dry season (October-March) and 55 in the rainy season (April-September). Porcupines used most habitats in proportion to their local availability, while selecting rock outcrop formations (possibly used as shelter sites) and avoiding open areas, wetlands and gallery forests. A mostly nocturnal behaviour was confirmed throughout the year, with some diurnal activity at the start and at the end of the rainy season. The importance of rains in determining birth peak has been also showed, with juvenile individuals always observed at the start and at the end of the rainy season. Full moon always inhibited activity of this large rodent, most likely evolved as an antipredatory behaviour to limit encounters with potential predators (common leopard Panthera pardus, spotted hyaena Crocuta crocuta and honey badger Mellivora capensis) and humans. Poaching pressure towards porcupines in West Africa is strong. Porcupines are killed for the traditional medicine, for their meat and because they are widely considered as a crop pest. This assessment should therefore be used as a basic tool to design conservation plans to preserve this rodent species in its native range.

Investigating the Effect of Flock Size on Vigilance in the American Coot (Fulica americana) in Relationship to Habitat

Among many anti-predator behaviors, vigilance is observed in many species and plays an important role in survival. In this study, we investigated the effect of flock size on vigilance in American Coots (Fulica americana)foraging on land and water, by observing individual birds in these habitats and recording the time spent scanning (i.e., vigilance). Mean flock size was larger on land compared to water and vigilance negatively correlated with flock size. Birds in water were more vigilant compared to on land, regardless of whether they were foraging alone or in flocks. However, the effect of flock size on vigilance showed a weak linear correlation as it was possible that other factors (e.g., human habituation, food kleptoparasitism, or scramble competition) could have also played a role in shaping vigilance. These results suggest that there is a relationship between flock size and vigilance, which are related to previous researches that show a negative correlation between vigilance and flock size. KEYWORDS: Birds; American Coot; Vigilance; Scanning; Foraging; Flock Size; Habituation; Competition; Behavior

Field observations of a cryptic agamid (Chameleon Dragon Chelosania brunnea Gray, 1845) in semi-arid savanna woodland of northern Australia

ABSTRACT Chameleon Dragons Chelosania brunnea Gray, 1845 are well known amongst naturalists of northern Australia as being one of the most cryptic and least frequently observed of Australia’s large, iconic lizards. Despite their broad distribution across the savanna woodlands that dominate northern Australia, very few records exist of this species and, as a consequence, nearly nothing is known about their natural history. Here, we present records of 19 Chameleon Dragons, detected during clearing activities of a small area of semi-arid woodland at Delamere Air Weapons Range, Northern Territory. Additionally, we provide notes on sexual dimorphism, antipredator behaviour and shelter site use in this species. We discuss how some of this novel information may explain why this species is so rarely detected and suggests that this cryptic agamid may be much more common in savanna woodland than currently appreciated.

ANALISIS KESTABILAN MODEL INTERAKSI PREDATOR-PREY DENGAN FUNGSI RESPON MONOD-HALDANE DAN PERILAKU ANTI PEMANGSA

This article examines a competing prey-predator model using the Monod-Haldane response function and anti-predator behavior. This article discusses equilibrium point determination, equilibrium point stability analysis, and numerical simulation. Obtained three equilibrium points, namely T1, T2, and T3, where the equilibrium-point is always saddle, the stability of the equilibrium points T2 and T3 will be stable if it meets the predetermined parameter requirements. There are two cases in the equilibrium point where the first case is vertically stable and the second case is spiral stable.

Effect of group size and experience on the ontogeny of sentinel calling behaviour in meerkats

Increased vulnerability to predation results in young individuals of many species experiencing higher predation pressure than adults. Consequently, the production of antipredator-related calls by young can differ from that of the same vocalizations given by adults. Sentinel behaviour is a coordinated vigilance behaviour, where one individual climbs on an elevated position and scans the surroundings for predators, while the rest of the group is mainly foraging. Meerkat, Suricata suricatta, sentinels produce six distinct sentinel call types, which inform other group members about the perceived predation risk, resulting in the adjustment of personal vigilance behaviour in foraging group members. Here, we investigated the onset of sentinel behaviour and the ontogeny of the different sentinel call types as well as the development of individual vocal signatures in meerkats. We found that meerkats started acting as a sentinel around 200 days of age, but this was highly dependent on group size, with individuals from smaller groups exhibiting sentinel behaviour earlier than individuals from larger groups. All six sentinel call types were already present in the repertoire upon first emergence of the behaviour; however, call rates of ‘all-clear’ calls increased while ‘warning’ calls decreased with increasing experience as sentinel. Analysis of one of the most frequent sentinel calls, the double note calls, indicated that fundamental frequency, mean amplitude, duration and entropy differed consistently between individuals, but we found no effect of age. Rather, our results provide evidence that individual signatures in this call type were already developed when young meerkats first started to act as sentinel and changed little with age. To conclude, we showed little ontogenetic change in overall sentinel behaviour as well as in its vocal coordination, indicating potentially high selection pressures on antipredator behaviours, such as the sentinel system, resulting in consistent behavioural responses upon first emergence.

Antipredator behaviour affected by prey condition, food availability and pH-mediated info-disruption

Prey around the world experience the risk of predation, and most have evolved constitutive and phenotypically plastic defences in response. Phenotypically plastic defences often come with trade-offs related to foraging, such that the magnitude of defence is mediated by body condition and food availability. Such adaptive responses are beneficial to prey, and there is an increasing appreciation that they can be disrupted by chemical compounds resulting from human activities. We examined predator-induced behaviours in freshwater snails (Physa acuta) using 32 combinations of different concentrations of olfactory predator cues, body condition and food availability to understand how they respond to the trade-off between avoiding predators and obtaining food. Using a subset of these conditions (16 environments), we then examined how snail responses were altered by increases or decreases in pH. We found that snails responded to increased predator cue concentrations with a shape consistent with a saturating response curve and that low body condition and low food availability weakened these responses. When we increased pH (from 7.8 to 9.5), snails exhibited weaker predator avoidance responses, but only in the absence of food. When we decreased pH (from 7.8 to 6.0), snails exhibited stronger predator avoidance responses and stronger declines in foraging, but only in the presence of food. Collectively, these results suggest that changes in pH due to acid mine drainage, eutrophication and ocean acidification may substantially alter the adaptive responses of aquatic animals. Future work should determine whether such info-disruption is common in other taxa, determine the underlying mechanisms and quantify the consequences of info-disruption to predator–prey and prey–resource interactions.

Impact of fear effect on plankton-fish system dynamics incorporating zooplankton refuge

In this paper, we analyze the impact of anti-predator behavior due to fear effect (K) and zooplankton refuge (r1) on a 3-D plankton-fish dynamical system involving phytoplankton, zooplankton, and fish species. We assume that zooplankton species have developed defense mechanisms against fish predation. The fear of fish predation altered anti-predator defenses, which affects the growth of the fish population. On the other hand, zooplankton refuge reduces fish induced mortality of zooplankton and plays a significant role in controlling phytoplankton growth. The density of fish species is suppressed in the presence of high refuge and the anti-predator response of zooplankton. It is determined that K and r1 can influence not only plankton-fish demography but also induce some mechanism to terminate planktonic blooms. Our mathematical study reveals that the low level of fear can stabilize the system dynamics in the presence of high rate of zooplankton refuge. Moreover, the low rate of zooplankton refuge can exclude complexity from the plankton-fish ecosystem in the presence of strong anti-predator responses of zooplankton. We have established the existence of all feasible biological equilibria and derived the conditional local and global stability of the given system around it. The Hopf-bifurcation analysis is carried out by considering K and r1 as bifurcation parameters. The direction of bifurcating solutions is also determined using the centre manifold arguments. Numerical simulation is carried out to substantiate our analytical findings.

Interactions Between Maternal, Paternal, Developmental, and Immediate Environmental Effects on Anti-predator Behavior of the Snail Physa acuta

Transgenerational plasticity, which occurs when the environment experienced by parents changes the phenotype of offspring, is widespread in animal and plant species. Both maternal and paternal environments can underlie transgenerational plasticity, but experimental studies unraveling how their effects interact together and with the personal (both developmental and immediate) environments are still rare. Yet unraveling these interactions is fundamental to understanding how offspring integrate past and present environmental cues to produce adaptive phenotype. Using the hermaphroditic and freshwater snail Physa acuta, we tested how predator cues experienced by offspring, mothers and fathers interact to shape offspring anti-predator behavior. We raised a first generation of snails in the laboratory with or without chemical predator cues and realized full-factorial crosses to disentangle maternal and paternal cues. We then raised the second generation of snails with or without predator cues and assessed, when adults, their escape behavior in two immediate environments (with or without predator cues) and activity in the immediate environment without predator cues. We found that personal, maternal, and paternal predator cues interacted to shape offspring escape behavior and activity. Firstly, for escape behavior, snails integrated the cues from developmental and parental environments only when exposed to predator cues in their immediate environment, suggesting that personal immediate experience must corroborate the risky parental environment to reveal transgenerational plasticity. For activity, this same hypothesis helps explain why no clear pattern of transgenerational plasticity was revealed, as activity was only measured without predator cues in the immediate environment. Secondly, a single maternal exposure to predator cues decreased offspring escape behavior while a single paternal exposure had no effect, surprisingly demonstrating sex-specific transgenerational plasticity for a simultaneous hermaphroditic species. Thirdly, when both mother and father were exposed, paternal cues were integrated by offspring according to their own developmental environment. The paternal exposure then mitigated the reduction in escape behavior due to the maternal exposure only when offspring developed in control condition. Overall, our study highlighted complex patterns of sex-specific transgenerational plasticity resulting from non-additive interactions between parental, developmental and immediate experiences.

Anti-predator behaviour depends on male weapon size.

Tonic immobility and escape are adaptive anti-predator tactics used by many animals. Escape requires movement, whereas tonic immobility does not. If anti-predator tactics relate to weapon size, males with larger weapons may adopt tonic immobility, whereas males with smaller weapons may adopt escape. However, no study has investigated the relationship between weapon size and anti-predator tactics. In this study, we investigated the relationship between male weapon size and tonic immobility in the beetle Gnathocerus cornutus. The results showed that tonic immobility was more frequent in males with larger weapons. Although most studies of tonic immobility in beetles have focused on the duration, rather than the frequency, tonic immobility duration was not affected by weapon size in G. cornutus. Therefore, this study is the first, to our knowledge, to suggest that the male weapon trait affects anti-predator tactics.

Diagnosing nest predators and anti-predator response of red wattled lapwing, Vanellus indicus (Boddaert, 1783)

Identification of nest predators and anti-predator behavior of Vanellus indicus (red wattled lapwings) were studied during two constitutive breeding periods (March-August) of 2018 and 2019. The study was performed along the river Ganges, Raebareli (Uttar Pradesh), India. The number of nesting pairs was counted by the line transect method and anti-predator responses were recorded by the focal sampling method. The nesting pairs varied significantly within and between study sites and years. A variety of predators (avian, mammalian and reptilian) were identified while some predators were designated in the unknown category. Sitting tight response was significantly different during the incubation period. The mobbing response, flying away and running away responses were significantly different during the post-incubation period. Circle noisily over the nests and alarm call were not significant between the two reproductive stages. We conclude that red wattled lapwings can differentiate among diverse predator species and adopt various anti-predator responses against them at different stages of their breeding cycle.

Do Female Songbirds Avoid a Mammalian Nest Predator When Selecting Their Nest Site?

Perceived predation risk can elicit strong behavioral responses in potential prey. During nest building, songbirds exhibit anti-predator behaviors under experimental conditions. Here, we hypothesized that females of two ground-nesting songbird species, the Ovenbird (Seiurus aurocapilla) and the Hermit Thrush (Catharus guttatus), would use naturally available cues of predation risk when selecting their nest site, thereby avoiding activity hotspots of Eastern Chipmunks (Tamias striatus), a predator on songbird nests and fledglings. Chipmunks are highly vocal, thus providing cues of their presence. We mapped chipmunk detections and songbird nests over four successive years in study plots located in mature deciduous forest of New Brunswick, Canada. Chipmunk activity varied by an order of magnitude among study plots and years. Nests were built further away from chipmunk detections than expected by chance in some, but not all, plot-year combinations. When comparing study plots, the proportion of nests built within hotspots of chipmunk activity was four times lower in the two plots where chipmunk activity was highest. Yet, we did not find clear evidence that chipmunk avoidance provided fitness benefits, possibly because this behavior procured little protection at high chipmunk densities. The persistence of this avoidance behavior in our focal species of ground-nesting songbirds might be linked to the benefits it procures at intermediate chipmunk densities.

Exposure to eagle owl feces induces anti-predator behavior, physiology, and hypothalamic gene responses in a subterranean rodent, the plateau zokor (Eospalax baileyi)

Predator odors are natural stressors that induce anti-predator defensive responses, which have developed under evolutionary pressures to maximize the fitness of an individual to avoid dangerous confrontations. In this study, we analyzed the defensive responses of a subterranean rodent species, the plateau zokor (Eospalax baileyi), to predation threat, and examined the trade-offs between defensive responses and foraging. Plateau zokors were exposed to 1, 3, and 6 g of eagle owl (Bubo bubo) feces, and the anti-predator behavioral, hormonal, and hypothalamic corticotropin-releasing factor and c-fos mRNA expression responses were analyzed and compared with the control (distilled water). Exposure of the animals to owl feces led to significant reductions in both duration of feeding and amount of food consumed, while some defensive behavioral responses (e.g., freezing and rearing) were more significant in the exposed animals than in the control. Serum levels of adrenocorticotropic hormone and corticosterone in plateau zokors exposed to owl feces were significantly higher compared with the control. The hypothalamic corticotropin-releasing factor and c-fos mRNA expression levels of plateau zokors exposed to 1, 3, and 6 g owl feces increased significantly, concomitant with the amount of eagle owl feces presented. Owl feces induced various behavioral, hormonal, and hypothalamic gene expression changes in plateau zokors exposed to them. Some behavioral and gene expression (but not hormonal) responses appeared to be threshold dependent. Predator odors supersede other signals and can provide comprehensive information to prey during life-threatening events. The plateau zokor is a typical subterranean rodent living in dark and enclosed subterranean habitats. Owing to this special habitat, zokors may be able to recognize ground predator odors and respond defensively. We investigated changes in behavior, hormones, and the hypothalamic corticotropin-releasing factor and c-fos mRNA expression levels of the plateau zokor when exposed to different amounts of eagle owl feces. We believe that our study makes a significant contribution to the literature because our results support the predation risk allocation hypothesis, showing that eagle owl feces inhibit foraging and induce various anti-predatory behavioral and neuroendocrine responses in plateau zokors.

Sex-specific plasticity across generations II: Grandpaternal effects are lineage specific and sex specific.

Transgenerational plasticity (TGP) occurs when the environment encountered by one generation (F0) alters the phenotypes of one or more future generations (e.g. F1 and F2). Sex selective TGP, via specific lineages or to only male or female descendants, has been underexplored in natural systems, and may be adaptive if it allows past generations to fine-tune the phenotypes of future generations in response to sex-specific life-history strategies. We sought to understand if exposing males to predation risk can influence grandoffspring via sperm in three-spined stickleback Gasterosteus aculeatus. We specifically tested the hypothesis that grandparental effects are transmitted in a sex-specific way down the male lineage, from paternal grandfathers to F2 males. We reared F1 offspring of unexposed and predator-exposed F0 males under 'control' conditions and used them to generate F2s with control grandfathers, a predator-exposed maternal grandfather (i.e. predator-exposed F0 males to F1 daughters to F2s), a predator-exposed paternal grandfather (i.e. predator-exposed F0 males to F1 sons to F2s) or two predator-exposed grandfathers. We then assayed male and female F2s for a variety of traits related to antipredator defence. We found little evidence that transgenerational effects were mediated to only male descendants via the paternal lineage. Instead, grandpaternal effects depended on lineage and were mediated largely across sexes, from F1 males to F2 females and from F1 females to F2 males. When their paternal grandfather was exposed to predation risk, female F2s were heavier and showed a reduced change in behaviour in response to a simulated predator attack relative to grandoffspring of control, unexposed grandparents. In contrast, male F2s showed reduced antipredator behaviour when their maternal grandfather was exposed to predation risk. However, these patterns were only evident when one grandfather, but not both grandfathers, was exposed to predation risk, suggesting the potential for non-additive interactions across lineages. If sex-specific and lineage effects are common, then grandparental effects are likely underestimated in the literature. These results draw attention to the importance of sex-selective inheritance of environmental effects and raise new questions about the proximate and ultimate causes of selective transmission across generations.

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.

Condition-dependent responses of fish to motorboats.

Anthropogenic noise is a pollutant of global concern that has been shown to have a wide range of detrimental effects on multiple taxa. However, most noise studies to-date consider only overall population means, ignoring the potential for intraspecific variation in responses. Here, we used field experiments on Australia's Great Barrier Reef to assess condition-dependent responses of blue-green damselfish (Chromis viridis) to real motorboats. Despite finding no effect of motorboats on a physiological measure (opercular beat rate; OBR), we found a condition-dependent effect on anti-predator behaviour. In ambient conditions, startle responses to a looming stimulus were equivalent for relatively poor- and good-condition fish, but when motorboats were passing, poorer-condition fish startled at significantly shorter distances to the looming stimulus than better-condition fish. This greater susceptibility to motorboats in poorer-condition fish may be the result of generally more elevated stress levels, as poorer-condition fish had a higher pre-testing OBR than those in better condition. Considering intraspecific variation in responses is important to avoid misrepresenting potential effects of anthropogenic noise and to ensure the best management and mitigation of this pervasive pollutant.

Impact of the Fear Effect on the Stability and Bifurcation of a Leslie–Gower Predator–Prey Model

In this paper, we investigate analytically and numerically the dynamics of a modified Leslie–Gower predator–prey model which is characterized by the reduction of prey growth rate due to the anti-predator behavior. We prove the existence and local/global stability of equilibria of the model, and verify the existence of Hopf bifurcation. In addition, we focus on the influence of the fear effect on the population dynamics of the model and find that the fear effect can not only reduce the population density of both predator and prey, but also destabilize the coexistence equilibrium, which are beneficial to the occurrence of limit-cycle-induced oscillation, or prevent the occurrence of limit cycle oscillation and increase the stability of the system.

Self-diffusion-driven pattern formation in prey–predator system with complex habitat under fear effect

In the present work, we explore the influence of habitat complexity on the activities of prey and predator of a spatio-temporal system by incorporating self-diffusion. First, we modify the Rosenzweig–MacArthur predator–prey model by incorporating the effects of habitat complexity on the carrying capacity and fear effect of prey and predator functional response. We establish conditions for the existence and stability of all feasible equilibrium points of the non-spatial model, and later we prove the existence of Hopf and transcritical bifurcations in different parametric phase-planes analytically and numerically. The stability of the spatial system is studied, and we discuss the conditions for Turing instability. Selecting suitable control parameter from the Turing space, the existence conditions for stable patterns are derived using the amplitude equations. Results obtained from theoretical analysis of the amplitude equations are justified by numerical simulation results near the critical parameter value. Further, from numerical simulation, we illustrate the effect of diffusion of the dynamical system in the spatial domain by different pattern formations. Thus, our model clearly shows that the fear effect of prey and predator’s functional response makes an anti-predator behaviour including habitat complexity which helps the prey to survive in the spatio-temporal domain through diffusive process.

Behavioral Reactions of Naturalized Ring-Tailed Lemurs (Lemur catta) to Native Owl Vocalizations

During routine surveys of owl distributions on St. Catherines Island, we observed naturalized ring-tailed lemurs displaying antipredator responses to owl auditory cues. In the 32 y since the introduction of ring-tailed lemurs to the island, two successful depredation events by two different owl species have been documented. We investigated the behavioral response of ring-tailed lemurs to determine if they responded consistently to social calls from all three owl species present on St. Catherines Island despite size differences among the owl species that could affect the likelihood of them serving as predators on ring-tailed lemurs. We observed while ring-tailed lemurs responded to all the auditory owl calls, they exhibited more intense, longer and more consistent responses to the two larger owl species – the barred owl and great horned owl – relative to the small Eastern screech owl. These data suggest naturalized species are capable of learning threat-sensitive antipredator behaviors to novel predator communities.

Ogre-Faced, Net-Casting Spiders Use Auditory Cues to Detect Airborne Prey

Prey capture behavior among spiders varies greatly from passive entrapment in webs to running down prey items on foot. Somewhere in the middle are the ogre-faced, net-casting spiders [1] (Deinopidae: Deinopis) that actively capture prey while being suspended within a frame web [2-5]. Using a net held between their front four legs, these spiders lunge downward to ensnare prey from off the ground beneath them. This "forward strike" is sensorially mediated by a massive pair of hypersensitive, night-vision eyes [5-7]. Deinopids can also intercept flying insects with a "backward strike," a ballistically rapid, overhead back-twist, that seems not to rely on visual cues [4, 5, 8]. Past reports have hypothesized a role of acoustic detection in backward strike behavior [4, 5, 8]. Here, we report that the net-casting spider, Deinopis spinosa, can detect auditory stimuli from at least 2m from the sound source, at or above 60 dB SPL, and that this acoustic sensitivity is sufficient to trigger backward strike behavior. We present neurophysiological recordings in response to acoustic stimulation, both from sound-sensitive areas in the brain and isolated forelegs, which demonstrate a broad range of auditory sensitivity (100-10,000Hz). Moreover, we conducted behavioral assays of acoustic stimulation that confirm acoustic triggering of backward net-casting by frequencies in harmony with flight tones of known prey. However, acoustic stimulation using higher frequency sounds did not elicit predatory responses in D.spinosa. We hypothesize higher frequencies are emitted by avian predators and that detecting these auditory cues may aid in anti-predator behavior. VIDEO ABSTRACT.

Experimental predator intrusions in a cooperative breeder reveal threat-dependent task partitioning

AbstractIn cooperatively breeding species, nonbreeding individuals provide alloparental care and help in territory maintenance and defense. Antipredator behaviors of subordinates can enhance offspring survival, which may provide direct and indirect fitness benefits to all group members. Helping abilities and involved costs and benefits, risks, and outside options (e.g., breeding independently) usually diverge between group members, which calls for status-specific differentiated behavioral responses. Such role differentiation within groups may generate task-specific division of labor, as exemplified by eusocial animals. In vertebrates, little is known about such task differentiation among group members. We show how breeders and helpers of the cooperatively breeding cichlid Neolamprologus savoryi partition predator defense depending on intruder type and the presence of dependent young. In the field, we experimentally simulated intrusions by different fish species posing a risk either specifically to eggs, young, or adults. We used intrusions by harmless algae eaters as a control. Breeders defended most when dependent young were present, while helper investment hinged mainly on their body size and on the potential threat posed by the respective intruders. Breeders and helpers partitioned defense tasks primarily when dependent young were exposed to immediate risk, with breeders investing most in antipredator defense, while helpers increased guarding and care in the breeding chamber. Breeders’ defense likely benefits helpers as well, as it was especially enhanced in the treatment where helpers were also at risk. These findings illustrate that in a highly social fish different group members exhibit fine-tuned behavioral responses in dependence of ecological and reproductive parameter variation.