Flight initiation distance of Urosaurus ornatus from the Sierra de Samalayuca, Mexico

In lizards, flight initiation distance (FID), the distance between a prey individual and a predator when escape begins, can be affected by numerous intrinsic and extrinsic factors, including sex, temperature, and level of conspicuousness. Here we report on a study of FID in a population of Ornate Tree Lizards, Urosaurus ornatus, from the Sierra de Samalyuca, Chihuahua, Mexico which are cryptic due to their dorsal coloration blending into their background. Urosaurus ornatus in our study population allowed close approaches (mean FID = 65 cm). Mean FID did not differ between males and females. We also found no effect of body, air, or substrate temperature on FID. The short FID we observed may be related to the cryptic nature of U. ornatus.

Predatory behaviour as a personality trait in a wild fish population

Consistent inter-individual differences in behaviour (i.e. animal personality variation) can influence a range of ecological and evolutionary processes, including predation. Variation between individual predators in commonly measured personality traits, such as boldness and activity, has previously been linked to encounter rates with their prey. Given the strong selection on predators to respond to prey, individual predators may also vary consistently in their response to prey in a manner that is specific to the context of predation. By studying wild piscivorous fish (pike cichlids, Crenicichla frenata) in their natural environment using experimental presentations of prey and control stimuli, we show that individual predators differ consistently in the amount of time spent near prey. Crucially, these differences were not explained by the behaviour of the same individuals in control presentations (the same apparatus lacking prey), suggesting that variation in the response to prey reflects a ‘predator personality trait’ which is independent from other individual traits (body size, boldness and/or neophobia) and environmental factors. Pike cichlids which spent more time near prey also attacked prey at a higher rate. These findings imply that the risk posed by individual predators cannot always be adequately predicted from typically studied axes of personality variation.

Startling predators

Startling signals are secondary defences that occur after the focal prey individual has been singled out for attack. Startling signals involve stimulation of the predator’s senses that cause it to delay or break off an attack. The assumption is that even a delay in attack can confer a survival advantage to the prey. This might occur because delay gives the prey an added opportunity to flee, or added opportunity for some other event to occur (perhaps the arrival of a predator of the predator) that causes the predator to break off the attack permanently. Startle signals influence the predator’s behaviour primarily through sensory and/or cognitive manipulation and must be separate from other mechanisms that may also influence predators’ behaviour so as to curtail, delay, or diminish an attack. We first consider the empirical evidence for the existence of such signals, before discussing the evolution of startle signals, the ecological aspects of this defence, co-evolutionary considerations, and suggestions for future research.

EFFECTS OF HUNTING AND ESCAPING BEHAVIOR ON AN ECOSYSTEM CONSISTING OF ONE-PREDATOR AND TWO-PREY SPECIES

In this study, we constructed a simple ecosystem consisting of one-predator–two-prey escape preferred strategy (EPS)- and hunting preferred strategy (HPS)-prey) — food for prey relationship to understand how the individual’s strategic behavior, hunting and escaping affects the ecosystem. In the model, when a prey encounters its predator and the food at the same time, either hunting or escaping should be taken as priority. Hunting priority is referred to as a HPS, while escape priority is referred to as an EPS. These strategies are associated with some degree of willingness to either hunt ([Formula: see text]) or escape ([Formula: see text]). In this model, two prey species were considered. One species (HPS-prey) takes HPS and the other rabbit species (EPS-prey) takes EPS. Predators take only HPS. Simulation results showed that the density of EPS-prey was obviously higher than that of HPS-prey in the appropriate values of [Formula: see text] and [Formula: see text] in the stable state. This means that when a prey individual has appropriate willingness for both hunting and escape, EPS is more beneficial for the survival than HPS. In addition, we briefly discussed the limitation of our model and the possible future improvements.

Foraging by red bats (Lasiurus borealis): do intraspecific chases mean territoriality?

Thirteen individually marked Lasiurus borealis concentrated their foraging around lights where insect densities were higher than in surrounding dark areas. The marked bats foraged for an average of 113.1 min per night, attacked an insect every 30 s, and captured, on average, 40% of the insects they attacked. This translated to a nightly food consumption of 6.2 g of insects, or 42% of the bats' body mass. The bats selected large (body length >10 mm) moths significantly more often than predicted by their availability, but the foraging activity of the bats did not significantly deplete the patches of prey. Individual L. borealis preferred certain lights within the feeding site and intraspecific chases were common, but there was no significant relationship between prey density and the incidence of chases, and the chases did not result in individuals being excluded from the feeding areas. Our data support the hypothesis that individual L. borealis eavesdrop on the echolocation calls of conspecifics to identify the presence of prey and that conspecific chases at feeding sites are not evidence of territorial behaviour.

FEEDING AND MATING IN THE INSECTIVOROUS CERATOPOGONINAE (DIPTERA)

The subfamily Ceratopogoninae (sensu Wirth, 1965a) is probably a natural (monophyletic) group but includes both blood sucking forms (Culicoidini) and predators on small insects. The insectivorous forms consist of a diversified array of six tribes and many genera represented in moist habitats throughout the world and especially abundant at lake margins.Many predator/prey observations are recorded. The prey consists almost exclusively of the males of other Nematocera or the smaller Ephemeroptera, which the female captures in flight by entering the male (mating) swarms of these insects and hovering until in a position to strike. The initial response is to the swarm-determining landmark, and the female hovers there whether or not potential prey is in flight; groups of hovering females can be induced artificially by suitable markers. These midges themselves form male swarms which the female enters for mating, and the unique method of hunting thus follows a pattern of behaviour already established in relation to another function. The insectivorous tribes have probably been derived from the more plesiomorphic Culicoidini, but the stages in the development of their radically different manner of hunting are not clear.The characteristic form of the mouthparts in the insectivorous genera is described and figured. The prey, after capture in flight, is usually held by the raptorial legs and quickly perforated by the mandibles. A proteolytic saliva is injected and the cellular tissue, except in the longer appendages, is liquefied and sucked out. In most species a single prey individual is not sufficient for one ovarian cycle, and the midge feeds several times. There is some degree of prey specificity, based at least in part on specific responses to the swarm-marker. In several genera there are long tubular "glands" in the abdomen, often everted in flight, whose function is not clearly established. Mobbing of the predator by the intended prey (mosquitoes) is described.The distinctive feature of mating is that the female, in addition to her other prey, often eats the male during mating. Nearly all the records come from the three tribes Heteromyiini, Sphaeromiini, and Palpomyiini. In these tribes (which probably form a relatively apomorphic monophyletic group) the male is usually a dwarf, and the plumose (auditory) antenna is more or less strongly reduced. It is suggested that the female remains in hunting phase when entering her conspecific swarm and captures the male as prey, and that the typical auditory recognition of female by male has become reduced or vestigial. In the more plesiomorphic tribes Ceratopogonini and Stilobezziini the male is normal in size and the antennal plume is fully developed, as in Culicoides, and there are only two records, at most, of the male being eaten during mating.The males eaten during mating are pierced through the head and reduced to an empty cuticle by the action of the lytic saliva. The terminalia however retain their hold, perhaps because of the early destruction of the suboesophageal ganglion, and the dry male cuticle often breaks away leaving the terminalia still attached. The structure of the terminalia and the mating position is described and discussed. Insemination is by spermatophore, which if the male is eaten never leaves the male duct. The terminalia of the male are inverted during mating and in some genera become so permanently early in adult life.An attempt is made throughout to view the phenomena in a phylogenetic context.Numerous illustrations are provided.