Anti-predator Device Research Articles

Are anal spines of anisopteran larvae an antipredator device? A case study in Boyeria irene (Odonata: Aeshnidae)

Are anal spines of anisopteran larvae an antipredator device? A case study in Boyeria irene (Odonata: Aeshnidae)

The call of the squeak beetle: bioacoustics of Hygrobia hermanni (Fabricius, 1775) revisited (Coleoptera: Hygrobiidae)

Hygrobiidae, or squeak beetles, originated in the Triassic-Jurassic and exhibit a relictual distribution in the Palaearctic, Oriental and Australasian regions. Hygrobiids are well known for their sound-producing abilities, although studies of their bioacoustics remain limited. Here we describe sound producing organs and bioacoustics of the Palaearctic Hygrobia hermanni (Fabricius, 1775). Plectra and pars stridens were examined in both sexes, and sound characteristics analysed. Despite small differences between male and female last abdominal ventrites, plectra were identical. Pars stridens, however, differed subtly, tooth ridges being wider in females. Calls of both sexes were harmonic, with peak frequency at 6.1 kHz, and secondary peak at 10.9 kHz; males exhibiting longer inter-chirp intervals. Calls changed with time in the laboratory, this possibly condition-related effect being more apparent in males. The differences found between sexes suggest that sound production in squeak beetles may function in intraspecific communication, in addition to being an antipredator device.

A spider that decorates its web perpendicular to the web plane

This paper examines and describes web decorating behavior by juveniles of the orb-weaving spider, Trichonephila antipodiana. Decorations consist of a three-dimensional ‘tube’ of silk line scaffolding within which detritus, prey items and moult exuviae are laid perpendicular to the web plane, extending from the central sticky web forward and backward to the dorsal and ventral barrier webs. Complementarity with barrier web construction, combined with the vulnerability of this ontogenetic stage, suggest that the primary function of the decorations is as an anti-predator device. Various lines of evidence support the view that the fundamental structural purpose of the decorations is perpendicular extension: (1) median web residency time was significantly greater for juveniles with decorations ≥ 1 cm in size; (2) detritus was the primary contributor to decoration length; and (3) examination of the in-laying technique for prey inclusions found them to be ‘unnecessarily’ dismembered and stretched out along the decorative plane. Although there is probably some degree of interdependence between predator avoidance and prey catching success, extension as a property fits most consistently within a defensive interpretation of function in so far as it confers either distance from and/or interference with predators.

Does the Threat of European Pine Marten (Martes Martes) Predation Influence the Height of Nests Built by Blue Tits (Cyanistes Caeruleus) and Great Tits (Parus Major)?

The major aim of this study was to examine the influence of the European Pine Marten ( Martes martes) predation on the heights of nests of Blue Tits ( Cyanistes caeruleus) and Great Tits ( Parus major) in nestboxes of different security levels. To this end we performed a comparison of nest heights before and after introducing an anti-predator device to two size-types of wooden nestboxes set up in a deciduous forest. Blue Tit and Great Tit nest sizes were influenced by the application of plastic entrance tubes as anti-predator devices that elongated a distance between the entrance and the interior of the nestbox. Nests were taller in nestboxes equipped with anti-predator devices regardless of nestbox size. Nests located in smaller nestboxes were destroyed by Martens more frequently than nests built in bigger nest boxes. Most nest functions in cavity-nesting birds, such as filling the excessive cavity space, maintenance of proper humidity, thermal, light and sanitary conditions for eggs and nestlings, improve with nest sizes. Because, in contrast, the risk of nest predation by martens increases with nest size (height within the nestbox), the nest predation constitute a major factor that constrains cavity-nesting birds in constructing tall nests.

Observation of threat behaviour by a pygmy skunk (Spilogale pygmaea) in Jalisco, Mexico

Skunks (Mephitidae:Carnivora) have well-devel-oped anal scent glands that emit a powerful secre-tion, used as an antipredator device. Species thatare chemically protected against predation oftenadvertise their noxiousness through visual, audi-tory, or olfactory warnings (Eisner & Grant1981), which are referred as aposematism.Skunks are aposematically coloured, and in addi-tion to their white and black colour pattern, theymay perform behaviours to identify themselves topotential predators (Lariviere & Messier 1996).The defensive behaviour of some skunks species(

Sentinels in Saltator atricollis (Passeriformes: Emberizidae).

I studied the existence of sentinels in Saltator atricollis in a 'campo-cerrado' (Brazilian savanna) during the breeding seasons of 1994-95 and 1995-96. Groups of this species consisted of two to seven birds (N = 25). Sentinels were present (mean +/- sd) 62% +/- 9% of the time, and most sentinel bouts lasted from less than one to six minutes (although in some occasions for more than 30 min.). Overlap of two or more sentinels occurred on average only 3.2% of the time with birds on guard. Sentinels commonly gave contact calls in the beginning and/or at the end of a sentinel bout. The group size had no effect on time with sentinels. However the encounter rate between raptors and groups significantly influenced the time guarded. The results of this study suggests that the ability of sentinels to detect predators may play a central role as an anti-predator device.

Biochemical characteristics and antibiotic properties of the mucous envelope of the queen parrotfish

Many species of wrasse (Labridae) and parrotfish (Scaridae) produce mucous cocoons at the beginning of each night. The mucus envelope which covers certain species of parrotfish throughout the night was first described by Winn (1955). The functional morphology of the slime producing gland has been investigated by Casimir (1971) and Lenke (1991). Large globlet cells in a folded epithelium form the opercular gland in the gill cavity under the operculum. The fish remain motionless inside the cocoon throughout the night. It is believed to be an antipredator device (Shephard, 1994). Parrotfish dash out of the mucous envelope when it is touched (J. J. Videler & G. J. Geertjes, pers. obs.) suggesting a function as an early warning system. A masking eVect for olfactory and tactile stimuli that could attract foraging common spotted moray eels Gymnothorax moringa (Cuvier) has been suggested (Winn & Bardach, 1956). It could also protect the fish from parasite settlement and the possibility of antibiotic properties has been predicted by Lenke (1991). Note that none of the functions mentioned are mutually exclusive. Whatever the function may be, it would require the cocoon to remain intact throughout the night at temperatures close to 30)C. A bactericidal eVect of the envelope could protect not only the cocoon but also the fish. Fish skin mucus has been targetted as a potential source in the search for novel antibiotics. It contains specific immunoglobulins, agglutins, lectins and lysins, especially lysozyme (Shephard, 1994). Antibacterial ion channel forming proteins from carp

Reduced tail regeneration in the Common Lizard, Lacerta vivipara, parasitized by blood parasites

1. Many lizards will lose their tail through autotomy as an antipredator device even though there must be significant costs during tail regeneration. 2. Parasites are energetically costly to the host, and may reduce the rate of cell regeneration. The relation between the presence of haemogregarines (phylum Sporozoa) and the rate of tail regeneration in the Common Lizard Lacerta vivipara (Jacquin) was examined. 3. Experimentally induced autotomy in parasitized lizards resulted in a significantly reduced rate of tail regeneration compared with non‐parasitized lizards. On the other hand, tail loss was not associated with an abnormal increase of parasite load, suggesting that the physiological stress (induced by tail loss) did not cause a decrease in parasite defence.

How important is the sting in insect social evolution?

A recent controversy has arisen over the relative advantage of the hymenopteran sting as a defensive weapon against vertebrates or invertebrates as this relates to the origin of insect sociality (STARR 1985a, KUKUK et al. 1989, and reply by STARR 1989). These studies emphasize the value of the sting as an antipredator device, but minimize its offensive potential. Concomitant with the evolution of cooperation among hymenopteran insects has been extensive exploitation by parasitic individuals of the reproductive efforts of others. Use of the sting is a common feature of both facultative and obligate nest usurpation in the social Hymenoptera. Increases in sting size and venom gland size have occurred, presumably as a result of arms races arising out of the competing selective forces of cooperation and parasitism which underly hymenopteran sociality.

Phenotypic plasticity of Daphnia pulex in the presence of invertebrate predators: morphological and life history responses.

Morphological and life history traits of two clones of the cladoceran Daphnia pulex were measured in the presence and absence of size-selective insect predators, the midge larva Chaoborus flavicans, which preys on small Daphnia, and the water bug Notonecta glauca, which preys on large Daphnia. The aim was to detect predator-induced phenotypic changes, particularly the effect of simultaneous exposure to both types of predators. Other work has shown that in the presence of Chaoborus americanus, Daphnia pulex produce a socalled neck spine which may carry several teeth. The morphological modifications are supposed to serve as an anti-predator device. Furthermore, females exposed to Chaoborus often delay their maturation; this has been interpreted as a cost that balances the benefits of the neck teeth. In this investigation, females of both clones produced fewer but larger offspring than control animals when reared in the presence of Chaoborus flavicans. The offspring showed the typical neck spine and delayed first reproduction. In the presence of Notonecta glauca, one of the clones produced more and smaller offspring, and maturation occurred at earlier instars. The other clone also produced more offspring than the control but there was no size difference. When both predators were present, in most cases the reactions of the daphnids were similar to those in the Notonecta experiment. The response to Chaoborus appeared to be suppressed. The observed modifications are interpreted as evolved strategies that reduce the impact of size-selective predation. They are consistent with predictions of life-history theory.

The other side of cyclomorphosis: Why Daphnia lose their helmets

While the possession of a helmet ap pears to be advantageous to many species of Daphnia as an antipredator device in summer, the fact that this structure is absent in spring suggests that during this time its formation is disadvantageous. Both helmeted and round‐headed individuals of Daphnia retrocurva occur simultaneously in Heney Lake, Quebec, in late May. Round‐headed individuals have significantly larger clutch sizes than do helmeted ones of the same carapace length at this time. The reproductive disadvantage of being helmeted seems to select for the round‐headed form in spring, when food levels are high and predation pressure is low.

ASPECTS OF THE BREEDING BIOLOGY AND ECOLOGY OF THE WHITEBELLIED SUNBIRD

Summary Earlé, R. A. 1982. Aspects of the breeding biology and ecology of the Whitebellied Sunbird. Ostrich 53:65-73. Breeding of the Whitebellied Sunbird Nectarinia talatala near Pietermaritzburg was recorded during six months of the year although males were capable of breeding for at least eight months. The same nest site was often used in consecutive years but the same nest was never used twice. 80,4 % of the nests built were between 0,6 and 1,s m off the ground. Nests built in thorny shrubs were the most successful but the highest percentage of nests were built in Prickly Pears Opuntia spp., which was probably an anti-predator device. Two colour-types of eggs were laid but the same female was always found to lay only one type. The greater majority of clutches consisted of two eggs (82,7%) but one and three egg clutches also occurred. Incubation started either after the first egg of a clutch was laid (64%) or after the second egg (36%). One case of double-broodedness was recorded. Incubating females most often left the nest to feed between 09h00 and 11h00.

Chaoborus americanus predation on various zooplankters; Functional response and behavioral observations

Predation rates for Chaoborus americanus on different types of noncyclomorphic zooplankton prey were determined in the laboratory as a function of both prey species and density. The sequence of events leading to consumption of prey was also observed, and probabilities determined for the various components.Predation rates generally reached an upper limit as the density of prey increased to high levels. Larger prey were always less vulnerable to Chaoborus predation. Among the species of zooplankton prey examined Holopedium gibberum suffered the lowest rates of predation, while those of the other plankters (Daphnia pulex, D. rosea, Moina hutchinsoni, Diaptomus birgei, D. leptopus, Cyclops vernalis) were approximately equivalent for any given size category.Observation of the predatory sequence indicates that for all the plankters except H. gibberum there were relatively high rates of evasion of attack by C. americanus and low rates of escape after capture. For H. gibberum the situation was reversed, and escape after capture was particularly important in determining the predation rate.The gelatinous envelope of Holopedium gibberum seems to operate as an effective anti-predator device which reduces the likelyhood of retention by Chaoborus after contact has been made.

Laboratory Encounters between Attending Desmognathus ochropaeus (Amphibia, Urodela, Plethodontidae) Females and Potential Predators

Confrontations were staged in the laboratory between attending (brooding) female salamanders and known or suspected predators. Females successfully defended their eggs against conspecific predators of various age and sex classes, and against ground beetles, but were not as successful against large heterospecific salamanders and ringneck snakes. A qualitative summary of these encounters is presented. Agonistic behavior by urodeles has been reported by several investigators, most recently Brandon and Huheey (1971); Brodie (1977); Dodd (1977); Thurow (1975). These reports suggest that agonistic behavior among urodeles may potentially serve as a form of social communication facilitating resource partitionment, or as an antipredator device. This paper examines the latter of these roles as manifested by the attending behavior of the mountain dusky salamander, Desmognathus ochrophaeus. With the exception of brief comments by Dennis (1962); Gordon (1952); Highton and Savage (1962); Tilley (1972), first hand published reports of the role of brooding female salamanders as an antipredator device are virtually absent from the literature. I have shown that parental care in D. ochrophaeus enhances survival of the clutch (Forester, 1974; MS). Here I describe qualitatively the encounters between attendants and selected predators. The observations suggest that the female varies her antagonistic response toward different potential predators, a phenomenon which warrants more thorough investigation.

Alarm response of the marine mud snail,Nassarius obsoletus: Specificity and behavioral priority

Nassarius obsoletus, N. vibex, andN. trivittatus were exposed to juices of conspecifics and taxonomically and ecologically related gastropod species. Conspecific juices caused the strongest alarm responses, while those from taxonomically related species (congeners) induced less pronounced responses. Juices from nonrelated species induced no alarm response with one notable exception, the strong alarm response ofN. trivittatus toUrosalpinx cinerea juices. Nonrelated gastropod species induced stronger feeding responses than more closely related species. The strongest feeding responses, however, were induced by juices from nongastropod mollusks. The apparent balance between feeding attraction to less related species and alarm response to more related species was further examined by manipulating the snails' diet. Starvation resulted in a great reduction of conspecific alarm responsiveness. Following the resumption of feeding, the original responsiveness was again observed. Although the alarm response is likely an antipredator device, conclusive evidence for its effectiveness in reducing predation is lacking. One of the predators ofNassarius obsoletus which may be responsible for maintenance of an alarm response is the green crab,Carcinus maenas.

La nidification des oiseaux en forêt gabonaise : Architecture, situation des nids et prédation

During a five year period data were collected on the location and the architecture of the nests of 110 species of rain forest birds in North East Gabon. 550 nests were observed, out of which 337 were followed until the departure of the fledglings or the disappearence of the eggs or nestlings. Many forest species make cryptic nests, some of which are built within bunches of dead leaves (Bleda sp.), others are disguised with dead plant material (Nectarinia sp. ; Malimbus sp.) or with caterpillar’s droppings and silk threads (Sylvietta denti). Warblers of genus Camaroptera conceal their nests between leaves which have been sawn together. The Bearded Greenbul Criniger barbatus incorporates into the rim of its nest the epiphytic fern Microgramma owariensis whose foliage remains green during the incubation of the eggs and the rearing of the young. Nicator chloris makes a loose nest «glued » on its support by rotten twigs ; the mycelium which develops in a few days securely binds the nest and its support. The location of many nests has apparently been selected in order to keep them from being located on the arboreal or terrestrial paths of predators : small trees isolated in the undergrowth, tips of horizontal twigs projecting above open spaces, tips of hanging lianas, branches overhanging water, intervals between the buttresses of the tree trunks, etc. Contrary to what frequently happens in temperate forests no attempt is generally made to conceal nests under foliage. More than two thirds of the nests discovered by the author were subsequently destroyed by predators or accidents. Whereas the concealment of the nest itself does not appear to be a very effective anti-predator device, the location of the nest is much more efficient : 70 % of nests located in the small trees of the undergrowth were destroyed as against 50 % of those built at the tip of projecting twigs, and 35 % of those overhanging water. Twenty per cent only of the nests located between buttresses were destroyed. A comparison is made with Maria Koepke’s observations in Eastern Peru. Unrelated species with similar ecological requirements usually have similar nesting habits. Some striking cases of convergence are mentioned between Galbulidae and Meropidae, Alcedinidae and Bucconidae, Tyrannidae and Nectariniidae, Icteridae and Ploceidae.

THE STABILIMENTUM OF THE ORB WEB SPIDER, ARGIOPE ARGENTATA: AN IMPROBABLE DEFENCE AGAINST PREDATORS

AbstractThe stabilimentum of orb web spiders is a structure for which several functions, both mechanical and defensive, have been suggested. Argiope argentata (Fabricius) builds a stabilimentum in the form of a white diagonal cross. Analysis of over 2500 webs of this species shows that the perfect cross is seldom built and nearly two thirds of the webs contain no stabilimentum at all. Experiments with wild birds as predators show that they can use stabilimentum-like models in prey location. From these data, and a review of the defensive adaptations of orb web spiders, it is argued that the A. argentata stabilimentum is not an anti-predator device. The evidence for a mechanical function is reviewed and discussed. It is suggested that the stabilimentum provides the spider with a means of making a final adjustment to the mechanical state of the web when this is necessary.

Erratic display as a device against predators.

Prey animals in many different taxonomic groups behave erratically when attacked by predators. This reaction is not accidental, but acts as a specific antipredator device. Observational data and theoretical considerations indicate that such protean displays function to confuse and disorient the predator and to increase its reaction time. Thus the survival of the prey is assisted, and the selective advntage whereby such erratic patterns of the prey animals may have evolved is created.

The Spines of Sticklebacks (Gasterosteus and Pygosteus) as Means of Defence Against Predators (Perca and Esox)

Feeding experiments with Pike (Esox lucius L.) and Perch (Perca fluviatilis L.) as predators, and Three-spined Sticklebacks (Gasterosteus aculeatus L.), Ten-spined Sticklebacks (Pygosteus pungitius L.), Minnows (Phoxinus phoxinus (L.)), Roach (Rutilus rutilus (L.)), Rudd (Scardinius erythrophthalmus (L.)) and Crucian Carp. (Carassius carassius (L.)) as prey species show that both species of stickleback enjoy a demonstrable degree of protection from these predators. This protection is much better for Gasterosteus than for Pygosteus; tests with de-spined sticklebacks show that it is mainly due to the spines. A description of the predatory behaviour of Perch and Pike is given; analysis of the experiments shows that (I) sticklebacks are rejected when, after being snapped up, their spines hurt the predator's mouth; (2) after very few experiences both Perch and Pike become negatively conditioned to the sight of sticklebacks and avoid them before they have made contact. As a result of this conditioning, the last links of the predators' feeding chain drop out; in Pike, mere fixation with two eyes was often sufficient to recognise the prey as unwanted. The possession of few and large spines in Gasterosteus must be regarded as more specialised than that of many small spines as found in various other species of stickleback. There is a correlation between the extreme development of this anti-predator device in Gasterosteus and (I) its boldness, (2) its tendency to select a more open nesting habitat, (3) the schooling and wandering tendencies of the females in the spawning season, and (4) its relatively conspicuous nuptial colours; these correlations suggest an interrelationship between anti-predator devices and reproductive behaviour and structures; the evolution of these two systems must have occurred in conjunction with each other.