For many benthic marine invertebrates, inversion (being turned upside-down) is a common event that can increase vulnerability to predation, desiccation and unwanted spatial transport, and requires behavioural ‘self-righting’ to correct. While self-righting behaviour has been studied for more than a century, the repeatability (R) – the portion of behavioural variance due to inter-individual differences – of this trait is not well understood. Heritability and the evolution of animal behaviour rely on behavioural repeatability. Here, we examined the self-righting technique of a cold-water holothurid, Parastichopus tremulus, and assessed the repeatability of this behaviour. Under laboratory conditions, P. tremulus consistently used muscle contractions to curl its body and roll itself back to an upright position, which provided for rapid (x̅ ± SD = 96.7 ± 49.8 s) and highly repeatable (R = 0.75) self-righting in the short term that varied between individuals (range of individual average righting times = 34.8–217.0 s). Righting time tended to increase with animal size; however, substantial variation was evident at comparable sizes, as average righting time ranged from 34.8–155.5 s for animals ~20 cm in body length. Contrary to previous studies on other echinoderms, we found no evidence of improved righting times for P. tremulus over time. This study ultimately provides the first detailed documentation of self-righting behaviour for P. tremulus and suggests that this species displays a high degree of repeatability for this trait in the short term.

Mosquito larvae have been shown to respond to water-borne kairomones from nearby predators by reducing their activity, and thus visibility. If they can identify the predator, they can then alter their response depending upon the associated predation risk. No studies have shown that mosquito larva may also detect water-borne vibrations from the predator. Final instar larvae of three mosquitoes: Culiseta longiareolata, Culex perexiguus and C. quinquefasciatus, were exposed to recorded vibrations from feeding dragonfly nymphs, to dragonfly kairomones and the combined effect of both. Predator vibrations caused C. longiareolata to significantly reduce bottom feeding and instead increased the more passive surface filter feeding. The larvae also significantly increased escape swimming activity. These behavioural changes were not significantly different from the effect of dragonfly kairomones, and there was no synergistic or additional effect of the two. C. perexiguus gave a smaller (but still significant) response to both dragonfly vibrations and to kairomones, probably due to a different feeding behaviour: when lying on the bottom, it was an inactive filter feeder. C. quinquefasciatus did not respond to either vibrations or kairomones and during these experiments was entirely an inactive surface filter feeder. Both C. longiareolata and C. perexiguus were thus able to detect and identify vibrations from feeding dragonfly nymphs as an anti-predator strategy. The lack of response in C. quinquefasciatus is probably a result of living in water that is highly polluted with organic material, where few predators can survive.

Here we report the use of Epinephelus itajara by Decapterus macarellus as a protection from Caranx latus predation attacks.

Although parasites are reported to alter host responses to predators, little is known about the neurochemical mechanisms involved. Using an odour preference test, we examined the effects of an acute, subclinical infection with the naturally occurring, single host, enteric protozoan parasite, Eimeria vermiformis, on the responses of male laboratory mice, Mus musculus, to a predator. Uninfected mice avoided the odour of a predatory cat, spending a minimal amount of time in a Y-maze in the vicinity of the cat odour. In contrast, mice infected with E. vermiformis, spent a significantly greater amount of time in the proximity of the cat odour, showing a reduced avoidance of the cat odour and a reduction in predator-induced fear or anxiety. This was not related to augmented opioid activity and decreased pain sensitivity in the infected mice, as neither treatment with the exogenous opiate, morphine, nor restraint stress-induced augmentation of endogenous opioid activity, had any significant effects on the responses of uninfected mice to cat odour. The altered responses of the infected mice to the cat odour were reduced by peripheral administration of the gamma-aminobutyric A (GABAA) antagonists, bicuculline and picrotoxin, but were not significantly affected by either the benzodiazepine antagonist, Ro 15–1788, the opiate antagonist, naloxone, or the excitatory amino acid, N-methyl-D-aspartate (NMDA) antagonist, MK-801. These results indicate that infection with E. vermiformis in mice reduces the avoidance of predator odour through neurochemical systems associated with anxiety involving, at least in part, GABAA receptor mechanisms.

Little information is available regarding predator-prey interactions in High-Antarctic coastal systems. In this study, the predation of Trematomus bernacchii (Pisces: Nototheniidae) on Adamussium colbecki (Mollusca: Pectinidae) is described and the related impact on the population structure of the mollusc is hypothesized. Fishes and scallops were collected during several expeditions between 1990/91 and 1997/98 summers, in nearshore waters at Terra Nova Bay (Antarctica). Adamussium colbecki was the main food item of T. bernacchii and an ontogenetic prey-size selection was observed. The predation was mainly on medium size classes of the scallop. These were lacking in the A. colbecki population sampled in the same period suggesting that the impact of fish-feeding on the size structure of the natural population of the mollusc may be substantial. Two size classes of the Adamussium population were not preyed on. Large adults avoid predation either because of the limits for mouth gape in the fish or by swimming avoidance capability, while smaller scallops may not be preyed upon because they are attached through byssus threads to very mobile large adults.

We characterized the day roost sites of four pairs and one solitary tawny frogmouth Podargus strigoides in a woodland in south-eastern Australia. The birds were equipped with radio transmitters which enabled us to locate them daily from autumn 1997 to late summer 1998. Tree species, tree size, roost height and orientation of the roosting bird were recorded. Over the study period tawny frogmouths frequented a large number of day roosts (up to 71 per pair). Birds rarely used the same roost over extended time periods and most roosts were used for less than 3 days. Mature trees with a girth of more than 0.5 m were preferred as day roosts. Tawny frogmouths exhibited a significant preference for the coarse and dark-barked stringybark trees, but other tree species such as the smooth-barked, light-coloured gums were also frequented. However, when roosting in gum trees, dead branches were preferred, presumably as these have a coarser appearance than living branches and therefore provided better camouflaging. Especially during winter, the birds showed a significant selection of branches on the northern side of roost trees presumably to maximize sun exposure. During summer, two pairs maintained a significant northerly preference, whereas the others used roosts with random orientations. Small-scale seasonal movements in the area used for day roosting were also observed, with two pairs selecting a distinct area with a south-westerly aspect during summer which appeared to have less sun exposure. Our study suggests that tawny frogmouths select roosts to (1) minimize visibility from day predators and (2) to facilitate passive thermoregulation by sun-basking.