Antipredator Tactics Research Articles

Courtship strategies of white-tailed deer and mule deer males when living in sympatry

Abstract Courtship behaviour reflects characteristics of an animal’s general biology, while also reflecting selective pressures specific to reproduction. Mule deer (Odocoileus hemionus) and white-tailed deer (O. virginianus) are sister species that differ in antipredator behaviour and sociality. We observed sympatric mule deer and white-tailed males to document their grouping patterns, courtship tactics, and aggressive interactions during the breeding season. Consistent with the hypothesis that courtship strategies reflect species differences in antipredator tactics and sociality, mule deer males were more likely than white-tailed males to tend females in multi male–multi female groups. White-tailed males almost exclusively tended females in isolated pairs and prevented other males from joining their groups. However, both species spent more time in isolated pairs as courtship advanced, likely to reduce competition. Our results enabled us to distinguish courtship behaviours that reflect contrasting antipredator tactics and sociality from courtship behaviours that reflect reproductive selective pressures that the species share.

Colour variation of a shell-brooding cichlid fish from Lake Tanganyika

The dwarf morph of Telmatochromis temporalis uses empty snail shells as shelters and spawning sites. This morph varies in body colour from pale to dark within populations. Pale individuals are likely to be cryptic on sandy-brown backgrounds through colour matching, but adaptive significance of dark individuals is unknown. The present study proposes two hypotheses for the occurrence of dark individuals: crypsis in darkness inside shells (darkness matching) and crypsis in irregular patterns consisting of shell shadows on sandy-brown backgrounds (pattern matching). The former hypothesis is less likely to be the main factor evolving dark bodies, because body darkness was not correlated with the amount of time that the fish remained within shells. Body darkness was correlated with shell density in their habitats, supporting the latter hypothesis because dark individuals may be able to mingle with shell shadows effectively at sites where shells were abundant. This study also found that body darkness was environmentally induced; therefore, this fish may shift between these anti-predator tactics (crypsis of pale individuals on sandy-brown backgrounds through colour matching and crypsis of dark individuals in irregular shadow patterns through pattern matching) by changing body darkness in response to shell density.

Evolutionary shifts in anti-predator responses of invasive cane toads (Rhinella marina)

A potential prey item’s response to encountering a predator depends on aspects of the predator (e.g., its locomotor capacity), the local environment (e.g., proximity to shelter) and the physiological state of the prey item, but in addition, anti-predator tactics also vary geographically among different populations within wide-ranging species. Using standardised trials, we tested responses of cane toads (Rhinella marina) to being placed on a laboratory runway and encouraged to flee. Overall, the toads least capable of rapid locomotion were the ones most likely to respond to simulated predator attack by exuding toxins rather than attempting to escape. A toad’s willingness to move down the runway and its propensity to exude toxin from the parotoid glands rather than fleeing were repeatable in successive trials and influenced by the animal’s location of origin, morphology, previous experience, and parentage. We found that specimens from Australia were more willing to flee than were those from the native range (French Guiana) or Hawai’i; larger toads, and those with relatively longer legs, were more willing to flee; captive-raised toads were less willing to flee and more willing to exude toxin. Captive-raised offspring resembled their wild-caught parents both in propensity to run and in propensity to exude toxin. Thus, geographic divergence among cane toad populations in anti-predator responses reflects a complex combination of processes, including both developmental plasticity and heritability. The process of colonising novel environments exposes an organism to a host of different predators that exert selection on morphology, behaviour and physiology. Over time, this can lead to the evolution of novel phenotypes that are adapted to local conditions. Anthropogenically facilitated biological invasions provide a unique opportunity to study how species respond to colonisation of new environments. Here, we studied geographic variation in cane toad (Rhinella marina) anti-predator behaviours from a range of locations (including invasive and native populations) using standardised trials. Our results suggest that invasive Australian cane toads have undergone a shift in their anti-predator response, becoming more willing to flee than are conspecifics from other areas. Location of origin, morphology, prior experience and parentage all played a role in shaping a toad’s anti-predator response, suggesting that the behaviour represents a combination of plastic and heritable variation.

Catch me if you can: antipredatory behaviour of chamois to the wolf

Antipredator behaviour is a multifactorial process – e.g. landscape features, escape tactics of prey, probability of encountering predators, predator type, age, sex and physical state of prey. Ungulates show a wide range of antipredator ploys. As reactions of mountain ungulates to their predators are still poorly understood, we hereby report on two interactions between Apennine chamois Rupicapra pyrenaica ornata and wolves Canis lupus in a protected area in the Central Apennines, Italy.Male and female chamois showed different reactions to the presence of the wolf. While females and juveniles fled to steeper, higher terrain upon the arrival of the wolf, males showed alternative antipredator tactics. In one case, the only male chamois present did not flee, but kept watching the movements of the wolf from a slab of rock at the foot of a steep scree, i.e. close to a potential escape terrain. In the other case, the two males present rushed to hide in the forest. Females formed a barrier between their kids and the wolf. Vigilance increased greatly, although chamois resumed their normal feeding activities within ca 10 min of the wolf visits. Fleeing of herd members in different directions may have helped to confuse the predator. In both cases, the antipredator behaviour of chamois proved successful to prevent predation.

Antipredator tactics are largely maternally controlled in goitered gazelle, a hider ungulate

Predation is usually the primary cause of infant death among ungulate species, with the annual variation in the survival of neonates over their first summer a major factor in the population dynamics of many ungulates. Consequently, the maternal rearing strategy of a species is crucial for its reproductive success. Since the roles mothers and fawns play in the implementation of antipredator strategies in hider species have been poorly understood until now, this paper considers this behavior in the goitered gazelle, which is a typical hider species. I found that within the first month after birth goitered gazelle mothers largely controlled the behavior of their fawns both during the active period (determining the timing of separation and reunion with fawns, movement direction and speed, and bed site location) and the hiding period (keeping the hiding fawns under continuous watch from a distance, especially right after birth). With age the fawns’ mobility increased and cases of independent behavior of fawns apart from their mothers were found more often, though females continued to control their fawns’ behaviors. The main elements of the goitered gazelles’ maternal care strategy − generally related to protecting fawns from potential predator attack − are very similar to other hider species in both bovids and cervids, which demonstrates a standard set of maternal care behaviors, irrespective of predator type or its behavioral peculiarities. Such maternal behaviors, however, likely only decrease the predation losses to a certain extent.

The effect of terrain and female density on survival of neonatal white-tailed deer and mule deer fawns.

Juvenile survival is a highly variable life‐history trait that is critical to population growth. Antipredator tactics, including an animal's use of its physical and social environment, are critical to juvenile survival. Here, we tested the hypothesis that habitat and social characteristics influence coyote (Canis latrans) predation on white‐tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) fawns in similar ways during the neonatal period. This would contrast to winter when the habitat and social characteristics that provide the most safety for each species differ. We monitored seven cohorts of white‐tailed deer and mule deer fawns at a grassland study site in Alberta, Canada. We used logistic regression and a model selection procedure to determine how habitat characteristics, climatic conditions, and female density influenced fawn survival during the first 8 weeks of life. Fawn survival improved after springs with productive vegetation (high integrated Normalized Difference Vegetation Index values). Fawns that used steeper terrain were more likely to survive. Fawns of both species had improved survival in years with higher densities of mule deer females, but not with higher densities of white‐tailed deer females, as predicted if they benefit from protection by mule deer. Our results suggest that topographical variation is a critical resource for neonates of many ungulate species, even species like white‐tailed deer that use more gentle terrain when older. Further, our results raise the possibility that neonatal white‐tailed fawns may benefit from associating with mule deer females, which may contribute to the expansion of white‐tailed deer into areas occupied by mule deer.

Signal Use by Octopuses in Agonistic Interactions

Cephalopods show behavioral parallels to birds and mammals despite considerable evolutionary distance [1, 2]. Many cephalopods produce complex body patterns and visual signals, documented especially in cuttlefish and squid, where they are used both in camouflage and a range of interspecific interactions [1, 3-5]. Octopuses, in contrast, are usually seen as solitary and asocial [6, 7]; their body patterns and color changes have primarily been interpreted as camouflage and anti-predator tactics [8-12], though the familiar view of the solitary octopus faces a growing list of exceptions. Here, we show by field observation that in a shallow-water octopus, Octopus tetricus, a range of visible displays are produced during agonistic interactions, and these displays correlate with the outcome of those interactions. Interactions in which dark body color by an approaching octopus was matched by similar color in the reacting octopus were more likely to escalate to grappling. Darkness in an approaching octopus met by paler color in the reacting octopus accompanied retreat of the paler octopus. Octopuses also displayed on high ground and stood with spread web and elevated mantle, often producing these behaviors in combinations. This study is the first to document the systematic use of signals during agonistic interactions among octopuses. We show prima facie conformity of our results to an influential model of agonistic signaling [13]. These results suggest that interactions have a greater influence on octopus evolution than has been recognized and show the importance of convergent evolution in behavioral traits.

Plastic response of fearful prey to the spatiotemporal dynamics of predator distribution.

Ecological theory predicts that the intensity of antipredator responses is dependent upon the spatiotemporal context of predation risk (the risk allocation hypothesis). However, most studies to date have been conducted over small spatial extents, and did not fully take into account gradual responses to predator proximity. We simultaneously collected spatially explicit data on predator and prey to investigate acute responses of a threatened forest ungulate, the boreal caribou (Rangifer tarandus), to the spatiotemporal dynamics of wolf (Canis lupus) distribution during spring. Movement analysis of GPS-collared individuals from both species revealed high plasticity in habitat-selection decisions of caribou. Female caribou avoided open areas and deciduous forests and moved relatively fast and toward foraging areas when wolves were closer than 2.5 km. Caribou also avoided food-rich areas only when wolves were within 1 km. Our results bridge the gap between long-term perceived risk and immediate flight responses by revealing dynamic antipredator tactics in response to predator proximity.

Cool Headed Individuals Are Better Survivors: Non-Consumptive and Consumptive Effects of a Generalist Predator on a Sap Feeding Insect.

Non-consumptive effects (NCEs) of predators are part of the complex interactions among insect natural enemies and prey. NCEs have been shown to significantly affect prey foraging and feeding. Leafhopper's (Auchenorrhyncha) lengthy phloem feeding bouts may play a role in pathogen transmission in vector species and also exposes them to predation risk. However, NCEs on leafhoppers have been scarcely studied, and we lack basic information about how anti-predator behaviour influences foraging and feeding in these species. Here we report a study on non-consumptive and consumptive predator-prey interactions in a naturally co-occurring spider–leafhopper system. In mesocosm arenas we studied movement patterns during foraging and feeding of the leafhopper Psammotettix alienus in the presence of the spider predator Tibellus oblongus. Leafhoppers delayed feeding and fed much less often when the spider was present. Foraging movement pattern changed under predation risk: movements became more frequent and brief. There was considerable individual variation in foraging movement activity. Those individuals that increased movement activity in the presence of predators exposed themselves to higher predation risk. However, surviving individuals exhibited a ‘cool headed’ reaction to spider presence by moving less than leafhoppers in control trials. No leafhoppers were preyed upon while feeding. We consider delayed feeding as a “paradoxical” antipredator tactic, since it is not necessarily an optimal strategy against a sit-and-wait generalist predator.

The ontogeny of morphological defenses in Kemp's ridley (Lepidochelys kempii) and loggerhead (Caretta caretta) sea turtles.

Marine turtles are large reptiles that compensate for high juvenile mortality by producing hundreds of hatchlings during a long reproductive lifespan. Most hatchlings are taken by predators during their migration to, and while resident in, the open ocean. Their survival depends upon crypticity, minimizing movement to avoid detection, and foraging efficiently to grow to a size too difficult for predators to either handle or swallow. While these behavioral antipredator tactics are known, changes in morphology accompanying growth may also improve survival prospects. These have been only superficially described in the literature. Here, we compare the similarities and differences in presumed morphological defenses of growing loggerhead (Caretta caretta) and Kemp's ridley (Lepidochelys kempii) posthatchlings, related species that differ in growth rate, timing of habitat shift (the return from oceanic to neritic locations), and size at maturity. In both species, vertebral spination and carapace widening increase disproportionally as small turtles grow, but later in ontogeny, the spines regress, sooner in ridley than in loggerhead turtles. Carapace widening occurs in both species but loggerheads are always longer than they are wide whereas in Kemp's ridley turtles, the carapace becomes as wide as long. Our analysis indicates that these changes are unrelated to when each species shifts habitat but are related to turtle size. We hypothesize that the spines function in small turtles as an early defense against gape-limited predators, but changes in body shape function throughout ontogeny-initially to make small turtles too wide to swallow and later by presenting an almost flat and hardened surface that large predators (such as a sharks) are unable to grasp. The extremely wide carapace of the Kemp's ridley may compensate for its smaller adult size (and presumed greater vulnerability) than the loggerhead.

Determinants of anti-predator tactics in hatchling grass snakes (Natrix natrix)

Many organisms exhibit diverse anti-predator tactics, influenced by genetics and prior experience. In ectothermic taxa, offspring phenotypes are often sensitive to developmental temperatures. If the effectiveness of alternative anti-predator responses depends on thermally sensitive traits, then the temperatures experienced during embryonic life should also affect how offspring respond to an approaching predator. We incubated 16 clutches of Swedish grass snakes (Natrix natrix) at a range of developmental temperatures, and scored body size, colour pattern, locomotor performance and anti-predator responses of 213 hatchlings from those clutches. A hatchling snake’s size and locomotor abilities were affected by its clutch of origin, its developmental temperature, and by an interaction between these two factors. Anti-predator tactics were strongly linked to locomotor ability, such that slower snakes tended to rely upon aggressive displays rather than flight. Incubation temperatures that generated slow (and thus aggressive) snakes also modified the colour of the snake’s nuchal spot. Temperatures in the low to medium range generated mostly cream, white and orange spots, whereas medium to high temperatures generated more yellow spots. Incubation effects, and gene X environment interactions, thus may generate complex correlations between morphology, locomotor ability, and anti-predator tactics.

Parental defence on the reef: antipredator tactics of coral-reef fishes against egg-eating seasnakes

On coral reefs in New Caledonia, the eggs of demersal-spawning fishes are consumed by turtle-headed seasnakes (Emydocephalus annulatus). Fish repel nest-raiding snakes by a series of tactics. We recorded 232 cases (involving 22 fish species) of antipredator behaviour towards snakes on a reef near Noumea. Blennies and gobies focused their attacks on snakes entering their nests, whereas damselfish (Pomacentridae) attacked passing snakes, as well as nest-raiders (reflecting territorial defence). Biting the snake was the most common form of attack, although damselfish and blennies also slapped snakes with the tail, or (blennies only) plugged the nest entrance with the parent fish's body. Gobies rarely defended the nest, although they sometimes bit or threw sand at the snake. A snake was more likely to flee if it was attacked before it began feeding rather than after it found the eggs (82% versus 3% repelled) and if bitten on the head rather than the body (68% versus 53%). Tail-slaps were not effective, although plugging the burrow and throwing sand often caused snakes to flee. These strong patterns reflect phylogenetic variation in fish behaviour (e.g. damselfish detect a snake approach sooner than do substrate-dwelling blennies and gobies) coupled with intraspecific variation in snake diets. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114, 415–425.

The role of refugia in reducing predation risk for Cape fur seals by white sharks

Refugia play an important role in shaping predator/prey interactions; however, few studies have investigated predator–prey relationships between large marine vertebrates, mainly due to the logistical challenges of studying marine species. The predictable interactions between Cape fur seals and white sharks in South Africa at two neighbouring seal colonies (Seal Island and Geyser Rock) with similar breeding conditions, but distinct adjacent seascapes, offer an opportunity to address this gap. Geyser Rock differs from Seal Island in being surrounded by abundant refugia in the form of kelp beds and shallow reefs, while Seal Island is mostly surrounded by deep open water. In this study, we compare data collected from Geyser Rock to the published data at Seal Island and ask, do seals adjust their anti-predator tactics as a function of landscape features? We found that during periods of high white shark presence, seals at Geyser Rock reduced their presence in open-water and utilized areas that contained complex landscapes around the colony. Although seals at Geyser Rock formed groups when traversing open water, neither group size (high risk median = 4, low risk median = 5) nor temporal movement patterns varied significantly with white shark presence as has been shown at Seal Island. Furthermore, recorded hourly predation rates at Seal Island were 12.5 times higher than at Geyser Rock. Together, these findings suggest that refuge use may be the more effective anti-predator response of seals to a seasonally abundant predator and that the predations at Seal Island reflect a comparative lack of refugia.

Maternal exposure to predator scents: offspring phenotypic adjustment and dispersal.

Predation is a strong selective pressure generating morphological, physiological and behavioural responses in organisms. As predation risk is often higher during juvenile stages, antipredator defences expressed early in life are paramount to survival. Maternal effects are an efficient pathway to produce such defences. We investigated whether maternal exposure to predator cues during gestation affected juvenile morphology, behaviour and dispersal in common lizards (Zootoca vivipara). We exposed 21 gravid females to saurophagous snake cues for one month while 21 females remained unexposed (i.e. control). We measured body size, preferred temperature and activity level for each neonate, and released them into semi-natural enclosures connected to corridors in order to measure dispersal. Offspring from exposed mothers grew longer tails, selected lower temperatures and dispersed thrice more than offspring from unexposed mothers. Because both tail autotomy and altered thermoregulatory behaviour are common antipredator tactics in lizards, these results suggest that mothers adjusted offspring phenotype to risky natal environments (tail length) or increased risk avoidance (dispersal). Although maternal effects can be passive consequences of maternal stress, our results strongly militate for them to be an adaptive antipredator response that may increase offspring survival prospects.

Observations of antipredator tactics among pantropical spotted dolphins (Stenella attenuata) attacked by smooth hammerhead sharks (Sphyrna zygaena)

Observations of antipredator tactics among pantropical spotted dolphins (<i>Stenella attenuata</i>) attacked by smooth hammerhead sharks (<i>Sphyrna zygaena</i>)

EFFECTS OF SEX, ENVIRONMENT, AND CONDITION ON THE MUSKING BEHAVIOR OF SYMPATRIC GARTERSNAKES (THAMNOPHIS SPP.)

Despite an abundance of studies documenting antipredator and defensive behaviors of gartersnakes (genus Thamnophis), few have quantitatively examined musking, a widely utilized antipredator tactic. In this study we quantify musking behaviors in the Terrestrial Gartersnake (Thamnophis elegans) and the Plains Gartersnake (T. radix) when hand-captured at four sites in and near Denver, Colorado, USA. Overall, Plains Gartersnakes musked significantly more often than Terrestrial Gartersnakes. Female Terrestrial Gartersnakes musked more frequently than males, a pattern not evident in the Plains Gartersnake. Additionally, we observed a positive correlation in body condition and musking propensity in Terrestrial Gartersnakes, suggesting resource-dependent behavior in this species. Musking behavior was consistent across variations in predation pressure, environmental conditions, and snake body size, all factors shown to influence other gartersnake defensive behaviors. These results corroborate other research which demonstrates that snake antipredator behaviors are determined by complex interactions of abiotic and biotic factors.

Pit-builder vs non-pit-builder: advantage of trap building strategy in antlion larvae does not mean greater behaviour diversity

Predators use different foraging modes, ranging from active to ambush predation. We investigated the predatory behaviour of two antlion species, the pit-builder Euroleon nostras and the non-pit-builder Neuroleon microstenus, both considered as ambush predators but with different predatory strategies. Since the pit-builders evolved from non-pit-builders, we focused on the similarities and differences in behavioural patterns and capture success. We found that most behavioural patterns occur in both species, although the non-pit-builder’s behaviour is less stereotypic and exhibits more behavioural patterns than in the pit-builder when comparing behaviour from prey introduction to jaw set without pit-construction. In N. microstenus, two distinct behavioural sequences were noted, which depend on the method of prey carcass clearing. This is the first report describing two methods of prey-carcass clearing in a non-pit-builder: tossing or dropping the prey. We also noted the presence of camouflage in the non-pit-builder, considered as an important mechanism in anti-predator tactics.

Phenotypic divergence between seasnake (Emydocephalus annulatus) populations from adjacent bays of the New Caledonian Lagoon

Populations of widespread species often differ in phenotypic traits, although rarely in such a dramatic fashion as revealed by research on turtle-headed seasnakes (Emydocephalus annulatus). These snakes are highly philopatric, with mark–recapture studies showing that the interchange of individuals rarely occurs even between two adjacent bays (separated by < 1.2 km) in Noumea, New Caledonia. Data on > 500 field-captured snakes from these two bays reveal significant differences between these two locations in snake morphology (mean body length, relative tail length, head shape), colour, ecology (body condition, growth rate, incidence of algal fouling), behaviour (antipredator tactics), and locomotor performance. For some traits, the disparity was very marked (e.g. mean swimming speeds differed by > 30%). The causal bases for these phenotypic divergences may involve founder effects, local adaptation, and phenotypic plasticity. The spatial divergence in phenotypic traits offers a cautionary tale both for researchers (sampling of only a few populations may fail to provide a valid overview of the morphology, performance, and behaviour of a species) and managers (loss of local populations may eliminate distinctive genetic variation).

Do invasive rodents impact endangered insular iguana populations?

Ample evidence confirms that large invasive mammalian competitors and predators can devastate endangered insular iguana populations. However, the impact of invasive rodents, particularly rats (Rattus rattus), has remained elusive. Tail autotomy occurs frequently in lizards, often as an antipredator tactic, but sometimes from intraspecific aggression. Tail autotomy can incur substantial locomotor, behavioral, energetic, and survival costs. Furcation (i.e., dividing into branches) of regenerated tails may also result from attempted predation but occurs much more rarely, and with unknown costs. To evaluate the potential impact of invasive rodents—primarily rats—on West Indian rock iguanas (genus Cyclura), we compared tail-break and tail-furcation frequencies among 19 insular iguana populations (3,537 individuals) representing three species in the Bahamian Archipelago (including the Turks and Caicos Islands). The findings supported our three hypotheses: (1) that tail-break and tail-furcation frequencies are significantly higher in populations coexisting with invasive rodents; (2) that tail-furcation results primarily from failed predation attempts rather than intraspecific aggression; and (3) that frequencies of tail breaks and tail furcation are associated with each other, suggesting a degree of commonality in cause-effect (i.e., failed predation attempts). Tail furcation, in contrast to tail breakage, never occurred on islands lacking invasive mammalian predators. We conclude that invasive rodents, particularly rats, may have a greater impact on endangered insular iguana species than previously recognized.

Tail waving in a lizard ( Bassiana duperreyi) functions to deflect attacks rather than as a pursuit-deterrent signal

Antipredator tactics that promote survival should be under strong selection. Therefore, apparently ‘risky’ behaviours should only be stably maintained in a population if they confer a fitness advantage. Here, we experimentally examined the adaptive function of tail waving, an apparently risky antipredator behaviour in hatchling Australian three-lined skinks, Bassiana duperreyi, by determining the effects of running speed, incubation temperature, sex and parental environment on the frequency of tail waving in laboratory trials. We found that hatchling running performance predicted tail-waving behaviour independent of the other factors, where slow individuals tail-waved more frequently than fast individuals. These data support the hypothesis that tail waving functions to deflect predatory attacks towards the tail, an expendable body part in this and other lizard species. Moreover, we suggest that tail waving in this species occurs as a ‘last resort’ in response to fatigue. In addition, our results allow us to reject the hypothesis that tail waving primarily functions as a pursuit-deterrent signal in hatchling B. duperreyi. Deflection is likely to have been the ancestral function of antipredator tail displays in lizards, with pursuit deterrence being a derived and less common function.