Dead Conspecifics Research Articles

The scent of cannibalism: The olfactory basis of cannibalism in hermit crabs

Animals are constantly exposed to sensory cues that provide conflicting information about their environments and must somehow rely on these sensory cues to make appropriate behavioral decisions. For cannibalistic scavengers, the odors of injured conspecifics or heterospecifics can serve as conflicting sensory cues because they could represent either the proximity of a food resource or the proximity of a predator (e.g., a recent predation event). Foraging cannibals must therefore weigh the risk–reward consequences of approaching injured conspecifics and heterospecifics. Previous research has shown that foraging cannibals respond to these conflicting cues by exhibiting caution, showing anti-predation behaviors instead of foraging behaviors. Hermit crabs are cannibalistic animals that rely heavily on olfaction to forage. Here I show for the first time that cannibalistic hermit crabs use the odors of crushed conspecifics and heterospecifics as foraging cues instead of anti-predation cues. Test animals, in general, responded to the odors of crushed conspecifics and heterospecifics with increased foraging responses instead of anti-predation responses, and readily consumed both conspecific and heterospecific animals. However, test animals showed faster approach times and longer feeding times for heterospecifics than conspecifics. These results suggest that hermit crabs are capable of discerning between the odors of conspecifics and heterospecifics, and show greater avoidance towards dead conspecifics than heterospecifics.

Death-associated odors induce stress in zebrafish

Living animals exploit information released from dead animals to conduct adaptive biological responses. For instance, a recently published study has shown that avoidance behavior is triggered by death-associated odors in zebrafish. Stress can clearly act as an adaptive response that allows an organism to deal with an imminent threat. However, it has not been demonstrated whether these chemical cues are stressful for fish. Here, we confirmed that dead zebrafish scents induce defensive behavior in live conspecifics. Additionally, we show for the first time in fish that these scents increase cortisol in conspecifics. To reach this conclusion, firstly, we exposed zebrafish to multi-sensorial cues (e.g., visual, tactile, chemical cues) from dead conspecifics that displayed defensive behaviors and increased cortisol. Also, when we limited zebrafish to chemical cues from dead conspecifics, similar responses arose. These responses coincide with the decaying destruction of epidermal cells, indicating that defensive and stress responses could take place as an effect of substances emanating from decaying flesh, as well as alarm substance released due to rupture of epidermal cells. Taken together, these results illustrate that living zebrafish utilize cues from dead conspecific to avoid or to cope with danger and ensure survival.

Dead heterospecifics as cues of risk in the environment: Does size affect response?

Organisms can minimize their exposure to risk of death or injury by assessing their environment and modifying their behavior accordingly. There is evidence that the current or recent presence of a predator introduces cues to the environment that organisms may use in risk assessment. However, we know little about whether terrestrial organisms use the remains of victims of predation as one such cue of elevated predation risk. A previous study showed that western scrub-jays (Aphelocoma californica) respond both to dead conspecifics and to encounters with a predator with alarm calling and aggregation (cacophonous aggregations), suggesting that they use dead conspecifics as indirect evidence of predation risk. Here we examine whether western scrub-jays also use dead heterospecifics as an indicator of risk. We find that jays respond with cacophonous aggregations to dead sympatric and allopatric jay-size heterospecifics but react weakly if at all to smaller heterospecifics. This suggests that size may be an important factor in determining whether a dead heterospecific is a relevant cue of risk. To our knowledge this is the first controlled experiment showing an animal using the visual cue provided by a dead heterospecific as an indicator of risk and communicating this risk to other conspecifics.

Use of chemical cues by coral reef animal larvae for habitat selection

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 19:231-238 (2013) - DOI: https://doi.org/10.3354/ab00532 Use of chemical cues by coral reef animal larvae for habitat selection David Lecchini1,2,*, Yohei Nakamura3 1USR 3278 CNRS-EPHE, CRIOBE, 98729 Moorea, French Polynesia 2Laboratoire d’Excellence ‘CORAIL’, 98729 Moorea, French Polynesia 3Graduate School of Kuroshio Science, Kochi University, 783 8502 Kochi, Japan *Email: lecchini@univ-perp.fr ABSTRACT: The present study explored the importance of chemical cues for habitat selection by fish (6 species), crustacean (1 species), and cephalopod (1 species) larvae in a 4-channel choice flume at Ishigaki Island, Japan. The larval attraction toward chemical cues from reef patches (seagrass bed patch, live coral patch, dead coral patch, and control water; Expt 1) and microhabitats within a given reef patch (live coral colonies, dead coral colonies, seagrass, and conspecifics; Expt 2) was tested in a 4-channel choice flume. The results in Expt 1 showed that 3 fish species used chemical cues to move significantly towards reef patches: Chromis viridis toward live coral patch water and Lutjanus fulviflamma and L. gibbus toward seagrass bed patch water. In Expt 2, 6 of 8 species (4 fishes, 1 cephalopod, and 1 crustacean) used chemical cues to move significantly toward conspecific water (Apogon properuptus, C. viridis, Dascyllus reticulatus, L. fulviflamma, Octopus cyanea, and Palaemonidae sp.). Overall, these results suggest that marine species can actively select settlement habitats according to olfactory cues (more specially, cues from conspecifics). Moreover, these results highlight the importance of conspecific cues over other types of information (reef patch and microhabitat) for habitat selection. Social aggregation of fish, crustacean, and cephalopod larvae with older conspecifics may be the result of individuals using conspecific ‘guides’ to potentially find beneficial resources (availability of resources and low mortality). KEY WORDS: Sensory mechanisms · Settlement cues · Fish · Crustacean · Cephalopod Full text in pdf format PreviousNextCite this article as: Lecchini D, Nakamura Y (2013) Use of chemical cues by coral reef animal larvae for habitat selection. Aquat Biol 19:231-238. https://doi.org/10.3354/ab00532 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 19, No. 3. Online publication date: October 24, 2013 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2013 Inter-Research.

Differential undertaking response of a lower termite to congeneric and conspecific corpses.

Undertaking behaviour is an essential activity in social insects. Corpses are often recognized by a postmortem change in a chemical signature. Reticulitermes flavipes responded to corpses within minutes of death. This undertaking behaviour did not change with longer postmortem time (24 h); however, R. flavipes exhibited distinctively different behaviours toward dead termites from various origins. Corpses of the congeneric species, Reticulitermes virginicus, were buried onsite by workers with a large group of soldiers guarding the burial site due to the risk of interspecific competition; while dead conspecifics, regardless of colony origin, were pulled back into the holding chamber for nutrient recycling and hygienic purposes. The burial task associated with congeneric corpses was coupled with colony defence and involved ten times more termites than retrieval of conspecific corpses. Our findings suggest elicitation of undertaking behaviour depends on the origin of corpses which is associated with different types of risk.

Observations of a free-ranging adult female dingo (Canis dingo) and littermates’ responses to the death of a pup

In contrast to several species of cetaceans and primates, behavioural responses to dead conspecifics have rarely been reported in wild canids. Here we provide details of the responses of an adult female and littermates to a dying and subsequently dead pup, including what appeared to be four instances of transport of the deceased pup by the mother over a two-day period, one of which was directly observed and filmed. We tentatively propose that, in the absence of any evidence of consumption of the pup, its transport by the mother could be interpreted as care-giving behaviour emanating from an enduring mother–infant bond, in a similar vein to what has been suggested for several other species exhibiting such behaviour.

Necrophobic behavior in small mammals

Necrophobic behaviors, defined as the avoidance of dead or injured conspecifics, have been formally documented in insects and aquatic organisms. It is plausible that such avoidance has been selected for by the risks of predation and disease that are associated with the presence of cadavers, and that necrophobic behaviors may be present across a variety of taxa. We demonstrate the avoidance of a house mouse (Mus musculus) cadaver by small mammals visiting experimental food trays, and by male and female house mice in a Y-maze exploration paradigm. In addition, we present individual differences in the responses of house mice to a house mouse cadaver. Further, we propose potential applications for the study of necrophobic behavior in improving wildlife management practices and models in disease ecology.

Effects of Tidal Elevation and Substrate Type on Settlement and Postsettlement Mortality of the Sydney Rock Oyster,Saccostrea glomerata, in a Mangrove Forest and on a Rocky Shore

Patterns of settlement and postsettlement mortality determine the distribution and abundance of sessile marine organisms. In mangrove forests and on rocky shores of eastern Australia, the Sydney rock oyster, Saccostrea glomerata, displays a pattern of declining abundance with increasing tidal elevation that might be related to or independent of the tidal elevation gradient in the substrate (bare, dead conspecifics, live conspecifics) available for attachment. We conducted parallel manipulative experiments on a rocky shore and in a mangrove forest to assess (1) the relative importance of tidal elevation and substrate type (bare, live oysters, or dead oysters) in determining the spatial distribution of new (<1 mm) S. glomerata recruits and (2) the contribution of settlement and postsettlement processes in setting patterns of spatial variation in established oyster populations. Patches of habitat with either live oysters, dead oysters, or no conspecifics were established at 3 tidal elevations at each site, and natural settlement and postsettlement mortality were monitored through time. At each site, and regardless of the substrate provided, we detected a similar pattern of fewer new S. glomerata recruits and greater postsettlement mortality on the high intertidal shore rather than the mid or low intertidal shore. Substrate type, by contrast, influenced the abundance of new recruits, but not subsequent postsettlement mortality. Consequently, over a period of months, direct effects of tidal elevation rather than effects of substrate type determined spatial patterns of oyster recruitment on the rocky shore and in the mangrove. Consequently, we documented that on a rocky shore and in a mangrove forest, settlement and early postsettlement mortality vary similarly across tidal elevation gradients and substrate types to determine the distribution of S. glomerata.

Social but not solitary bees reject dangerous flowers where a conspecific has recently been attacked

Social bees are known to avoid inflorescences marked with dead conspecifics or their smell. The avoidance response could be triggered by alarm signals actively given by attacked bees or by substances passively released through injuries as a by-product of the attack. To discriminate between these two options we note that both social and solitary bees are expected to react to nonsignalling cues associated with predation risk, while only social bees are expected to give alarm signals. We simulated risky inflorescences by pinching a landing bee with forceps, and compared the rate at which bees visited these experimental inflorescences and unmanipulated control inflorescences. We conducted the experiment with four species of social bees, Apis mellifera, Apis dorsata, Apis florea and Bombus terrestris and with three species of solitary bees, Eucera sp., Panurgus sp. and Nomia strigata. We found that while the three species of solitary bees responded similarly to control and experimental inflorescences, all four species of social bees strongly rejected inflorescences where we simulated a predation attempt. The finding that only social species avoided landing on dangerous inflorescences strongly suggests that the release of the alarm cue has been selected for its signalling value in social bees.

Western scrub-jay funerals: cacophonous aggregations in response to dead conspecifics

All organisms must contend with the risk of injury or death; many animals reduce this danger by assessing environmental cues to avoid areas of elevated risk. However, little is known about how organisms respond to one of the most salient visual cues of risk: a dead conspecific. Here we show that the sight of a dead conspecific is sufficient to induce alarm calling and subsequent risk-reducing behavioural modification in western scrub-jays, Aphelocoma californica, and is similar to the response to a predator (a great horned owl, Bubo virginianus, model). Discovery of a dead conspecific elicits vocalizations that are effective at attracting conspecifics, which then also vocalize, thereby resulting in a cacophonous aggregation. Presentations of prostrate dead conspecifics and predator mounts elicited aggregations and hundreds of long-range communication vocalizations, while novel objects did not. In contrast to presentations of prostrate dead conspecifics, presentations of a jay skin mounted in an upright, life-like pose elicited aggressive responses, suggesting the mounted scrub-jay was perceived to be alive and the prostrate jay was not. There was a decrease of foraging in the area during presentations of prostrate dead conspecifics and predator mounts, which was still detectable 24 h later. Foraging returned to baseline levels 48 h after presentations. Novel objects and mounted jays did not affect foraging. Our results show that without witnessing the struggle and manner of death, the sight of a dead conspecific is used as public information and that this information is actively shared with conspecifics and used to reduce exposure to risk.

Temperature mediates non-competitive foraging in indigenous rock (Cancer irroratus Say) and recently introduced green (Carcinus maenas L.) crabs from Newfoundland and Labrador

The green crab, Carcinus maenas, was recently (2007) introduced to predominantly cold water ecosystems of Newfoundland and Labrador (NL). The known broad diet of the green crab in warmer ecosystems of the northwest Atlantic raised concerns about its ability to interfere with species indigenous to NL, especially the rock crab, Cancer irroratus, which exhibits common preference with the green crab for the blue mussel, Mytilus edulis. We used two experiments to determine the effects of low water temperature representative of southern NL (4°C and 12°C), body size (small, medium, and large), chela loss, and chemical cues from live and dead conspecifics and heterospecifics on capture and selection of blue mussels in six size classes (10 to 40mm in shell length) and five associated behaviors (handling, feeding, sitting, moving, and burying in sediments or using an artificial cavity) in rock and green crabs from NL held individually in microcosm tanks. Experiment 1, which addressed the effects of changes in water temperature, body size, and chela loss on foraging in both rock and green crabs, indicated that mussel capture was nearly three times higher in large than small individuals in both species. Large rock and green crabs captured between 43 and 46% of the largest (>30mm) mussels, while small rock and green crabs captured 25 and 76% of the smallest (<20mm) mussels, respectively. Chela loss caused a twofold decrease in mussel capture in rock crabs, though did not affect green crabs. Experiment 2, which addressed the effects of changes in water temperature and chemical cues on foraging in rock crabs, showed that cues from rock crabs (live and dead) and green crabs (live) had no effect on mussel capture, while causing only subtle changes in mussel size selection. However, small rock crabs buried in sediments or were located within the artificial cavity twice as often in the presence of cues from dead rock crabs than in the absence of cues. Overall, the crabs captured approximately three times more mussels at 12°C than 4°C regardless of crab species, crab size, chela loss, and the presence or absence of chemical cues, which therefore demonstrate the pervasive effect of low temperature on foraging in both rock and green crabs. We conclude that the recent introduction of the green crab to Newfoundland and Labrador may have a greater impact on foraging in small than large rock crabs and those missing one chela, while altering mussel populations through marked preference by small green crabs for small mussels.

Death among geladas (Theropithecus gelada): a broader perspective on mummified infants and primate thanatology

Despite intensive study in humans, responses to dying and death have been a neglected area of research in other social mammals, including nonhuman primates. Two recent reports [Anderson JR, Gillies A, Lock LC. 2010. Pan thanatology. Current Biology 20:R349-R351; Biro D, Humle T, Koops K, Souse C, Hayashi M, Matsuzawa T. 2010. Chimpanzee mothers at Bossou, Guinea carry the mummified remains of their dead infants. Current Biology 20:R351-R352] offered exciting new insights into behavior toward dying and dead conspecifics in our closest living relatives-chimpanzees. Here, we provide a comparative perspective on primate thanatology using observations from a more distant human relative-gelada monkeys (Theropithecus gelada)-and discuss how gelada reactions to dead and dying groupmates differ from those recently reported for chimpanzees. Over a 3.75-year study period, we observed 14 female geladas at Guassa, Ethiopia carrying dead infants from 1 hr to ≥48 days after death. Dead infants were carried by their mothers, other females in their group, and even by females belonging to other groups. Like other primate populations in which extended (>10 days) infant carrying after death has been reported, geladas at Guassa experience an extreme climate for primates, creating conditions which may favor slower rates of decomposition of dead individuals. We also witnessed the events leading up to the deaths of two individuals and the responses by groupmates to these dying individuals. Our results suggest that while chimpanzee mothers are not unique among primates in carrying their dead infants for long periods, seemingly "compassionate" caretaking behavior toward dying groupmates may be unique to chimpanzees among nonhuman primates (though it remains unknown whether such "compassionate" behavior occurs outside captivity).

Interpreting odours in hermit crabs: A comparative study

Odours of different sources can indicate to hermit crabs the availability of empty shells, crucial resources for the life cycle of almost all of them. Here, we compared Clibanarius erythropus and Pagurus bernhardus for the intensity of investigative behaviour exhibited towards an empty, well-fitting shell in the presence of (1) plain seawater as control and seawater conditioned by (2) dead and live snails, (3) dead and live conspecifics, (4) live predators, and (5) food. During 10 min of observation, we recorded latency (the time until the first contact with the shell), and the number and duration of shell investigation bouts. The two species behaved similarly when exposed to the odours of food, live snails, and predators, while a more intense shell investigation was induced by dead snail odour in C. erythropus and by dead or live conspecific odour in P. bernhardus. Further studies should investigate the influence of phylogeny and ecology on this interspecific difference.

Visual cues used by ant-like jumping spiders to distinguish conspecifics from their models

Despite the conceptual appeal of how morphological mimics visually distinguish between conspecifics and their models, scant attention has been given to this topic. Accurate discrimination between ants and conspecific spiders is likely to be under strong selection because approaching an ant may result in the spider's death, while approaching a different sex conspecific may result in copulation. I addressed this question by examining responses of the ant-like jumping spider Myrmarachne bakeri Banks 1930 (Salticidae) toward motionless, odorless lures made from dead conspecifics, ants, or lures using components of non-ant-like salticids, ant-like salticids and ants. I found that chelicerae, legs I and body, but not movement, are important cues used by M. bakeri to distinguish conspecifics from ants, but the relative importance of these cues differs depending on a spider's sex. Batesian mimicry is possibly the best-documented example of a deceitful signal, and while the effects of these signals on predators have received considerable attention for over a century (Bates 1862; Wickler 1968; Ruxton et al. 2004) there is scant information on the effects of mimetic signals on conspecifics. This gap in our knowledge is not reflected in the importance of the issue at hand: Batesian mimics resemble an unpalatable or dangerous model, and mimicry has evolved due to its effect on potential predators, which consequently avoid the mimic (Edmunds 1974). However, all animals capable of processing information in the specific sensory modality of the mimetic signal may be fooled by mimics- not just predators. Consequently, if a mimic is a visually guided animal, and it looks like its model, conspecifics themselves may be fooled about its identity. This may be especially pertinent if the model is dangerous to the mimic itself.

Cannibalism in the Australian Pelican (Pelecanus conspicillatus)and Australian White Ibis (Threskiornis molucca)

We provide first evidence of cannibalism in fledglings of the Australian White Ibis (Threskiornis molucca) and Australian Pelican (Pelecanus conspicillatus). The ibis only fed on carcasses of dead conspecifics (indirect cannibalism); the pelican consumed live pelican (heterocannibalism) and ibis nestlings.

Feeding behaviour in the Antarctic fairy shrimp, Branchinecta gaini

Direct observations of feeding behaviour in Branchinecta gaini are described. B. gaini possess sophisticated food manipulation behaviours, using their abdominal appendages to ‘scrape’ at and carry away food items. Scraping behaviour was employed by animals for both detrital feeding and the cannibalisation of dead conspecifics. In the absence of like observations from other non-raptatory species of Branchinecta, it appears that adults of B. gaini occupy an intermediary position between species that feed exclusively on vegetative and detrital material and those (e.g. B. gigas, B. ferox, B. raptor) that are known to be carnivorous. In an Antarctic context, particularly, specialisation towards carnivory would have little adaptive value, while expansion of diet breadth via increased manipulative and digestive flexibility would, on the other hand, be advantageous. These behaviours, moreover, mean that B. gaini plays an active role in the breakdown and recycling of its own nutrient base.

Disease transmission by cannibalism: rare event or common occurrence?

Cannibalism has been documented as a possible disease transmission route in several species, including humans. However, the dynamics resulting from this type of disease transmission are not well understood. Using a theoretical model, we explore how cannibalism (i.e. killing and consumption of dead conspecifics) and intraspecific necrophagy (i.e. consumption of dead conspecifics) affect host-pathogen dynamics. We show that group cannibalism, i.e. shared consumption of victims, is a necessary condition for disease spread by cannibalism in the absence of alternative transmission modes. Thus, endemic diseases transmitted predominantly by cannibalism are likely to be rare, except in social organisms that share conspecific prey. These results are consistent with a review of the literature showing that diseases transmitted by cannibalism are infrequent in animals, even though both cannibalism and trophic transmission are very common.

Cachers, Scavengers, and Thieves: A Novel Mechanism for Desert Rodent Coexistence

A biologically explicit simulation model of resource competition between two species of seed-eating heteromyid rodent indicates that stable coexistence is possible on a homogeneous resource if harvested food is stored and consumers steal each other's caches. Here we explore the coexistence mechanisms involved by analyzing how consumer phenotypes and presence of a noncaching consumer affect the competitive outcome. Without cache exchange, the winning consumer is better at harvesting seeds and produces more offspring per gram of stored food. With cache exchange, coexistence is promoted by interspecific trade-offs between harvest ability, metabolic efficiency, and ability to pilfer defended caches of heterospecifics or scavenge undefended caches of dead conspecifics or heterospecifics. Cache exchange via pilferage can equalize competitor fitnesses but has little stabilizing effect and leads to stable coexistence only in the presence of a noncaching consumer. In contrast, scavenging is both equalizing and stabilizing and promotes coexistence without a third consumer. Because body size affects a heteromyid rodent's metabolic rate, seed harvest rate, caching strategy, and ability to steal caches, interspecific differences in body size should produce the trade-offs necessary for coexistence. The observation that coexisting heteromyids differ in body size therefore indicates that cache exchange may promote diversity in heteromyid communities.

Shell acquisition by hermit crabs: which tactic is more efficient?

Gastropod shells are limited resources for most hermit crab species, acting as primary factors in various aspects of their biology. To investigate the efficacy of different behavioral tactics adopted for their acquisition (locomotion, attendance at shell-supplying sites, interactions with conspecifics in aggregation) we conducted observations and experiments at a salt marsh in New England (USA). Locomotion, fast and meandering, significantly increased the chances of encountering empty shells and conspecifics. However, shell exchanges were rare. Simulated gastropod predation sites quickly attracted a larger number of hermit crabs than the other shell-supplying sites tested (live and dead conspecifics, live snails) and induced the rapid occupancy of all the empty shells offered, usually by the first crabs arriving at the site. Aggregations seemed not to function as shell exchange markets, as previously suggested for several other species. In the short run, exploitation seems to be more efficient for the acquisition of new shells by Pagurus longicarpus. In the long run, it is the density of nondestructive gastropod predators that regulates the availability of new shells of good quality in the pool available to this hermit crab species.

The role of cannibalism and contaminant source on bioaccumulation in aquatic food webs

Two aspects of bioaccumulation in an aquatic food web are explored. First, the possible implications of cannibalism, including the scavenging of conspecifics, as a factor influencing food web bioaccumulation and biomagnification are explored by examining the behavior of total polychlorinated biphenyls (PCBs) in a simple aquatic food web consisting of plankton, juvenile and adult Mysis relicta, Diporeia, and alewife. From an analysis of trophic transfer efficiencies and food consumption rates, it is concluded that, for M. relicta, a maximum extent of cannibalism in a population is about 10%, although certain individuals may be more cannibalistic. The model suggests that cannibalism and scavenging of dead conspecifics generally result in an increase in concentration by self-biomagnification, but the effect is small and unlikely to exceed 5% on the average. Concentration differences also are likely to result from changes in the relative amounts of the dietary components. Highly cannibalistic individuals may achieve higher levels of bioaccumulation. In extreme cases, the food web model becomes mathematically unstable because of excessive feedback of high concentrations. A major implication is that differences in extent of cannibalism and scavenging probably contribute significantly to natural concentration variation in a population. Second, and more important, is the effect of benthic versus pelagic sources, especially when significant fugacity differences exist between these zones. A simple method is described by which the separate contributions from these sources can be estimated for organisms at higher trophic levels.