Davide Csermely

Agonistic behaviour in grouped sows. II. How social rank affects feeding and drinking behaviour.

Abstract Groups of sows housed in pens with concrete floor were observed to detect differences in feeding and drinking behaviour between animals of high‐ and low‐rank. Dominant individuals remained at the centre of the mash pile defending the food against other animals. The total time spent feeding was similar in high‐ and low‐ranking sows. However, the high ranking sows interrupted feeding more often; subordinates stopped feeding for longer periods because they retreated from attacks. As the mash began to disappear the low‐ranking sows resisted the dominants’ attacks and refused to leave the feeding area. Drinking behaviour was very frequent in subordinate sows in the early minutes of the meal; this is probably a redirected behaviour resulting from the frustration of being not able to feed continuously.

Lateralization in the predatory behaviour of the common wall lizard (Podarcis muralis)

Ectotherms have been shown being lateralized as well as mammals and birds. This is particularly evident in visual lateralization, i.e. the different use of the eyes, leading to use a specific eye to observe specific kind of stimuli and to process them with the correspondent contralateral hemisphere. Several lower vertebrates are facilitated in this from the lateral position of the eyes, enabling them to carry out more tasks simultaneously, controlled by different eyes and relative hemispheres. Predatory responses seem usually mediated by the right eye/left hemisphere in fishes, amphibians and some sauropsids, but there are no strong evidences of this in lizards. Eighteen wild males of the Common wall lizard Podarcis muralis were tested individually in captivity to ascertain whether they are lateralized to look at prey with a specific eye. The lizards were gently induced entering a 30-cm long central arm of a T-maze which led to a 44.5-cm long arm cross-arm at whose extremities there were two identical prey, Tenebrio molitor larvae, familiar to the lizards. We recorded what direction the lizards chose to reach the prey and the frequency and duration of head turning, indicative of looking either prey with the left or the right eye. We found that individuals show being lateralized at individual level. The preferred direction taken to reach the prey is the right for the majority of those (4 of 5) showing an evident preference, indicating also a possible form of laterality at population level. In addition, lizards maintained the same head side of the direction taken turned for more time towards the prey than the opposite head side, revealing an eye preference for observing this kind of cue. Our study demonstrates how males of Podarcis muralis have a visual lateralization to capture prey. Furthermore, it is another support to the hypothesis of vertebrate lateralization derivation from a common ancestor.

Prey killing by Eurasian Kestrels: the role of the foot and the significance of bill and talons

Csermely, D., Berte, L. and Camoni, R. 1998. Prey killing by Eurasian Kestrels: the role of the foot and the significance of bill and talons. - J. Avian Biol. 29: 10-16. The technique used by birds of prey to kill their quarry has rarely been described in detail. Although it is common to watch a raptor hunting, distance and natural obstacles normally prevent the observer from observing what actually happens to the prey after being grasped by the bird. Therefore, we studied the predatory sequence and killing technique displayed by a sample of ten wild Eurasian Kestrels temporarily held in captivity because of various injuries. They were offered individually either a laboratory mouse or young laboratory rat. Direct observation was complemented by necropsy of the prey confirming that bill strikes frequently observed after grasping the prey are not used to kill it but merely to damage its central nervous system thereby minimising escape attempts. Furthermore, talons are not used as weapons at all, but only as tools that elongate the toes to hold the quarry more firmly. In contrast, several signs indicating death by suffocation were regularly found and these were confirmed by inspection of rodents sacrificed by CO2. We also discuss a hypothesis explaining the adaptive and evolutionary significance of the kestrels use

Escape-reaction of captive young red-legged partridges (Alectoris rufa) reared with or without visual contact with man

Abstract It was noted that adult birds of Alectoris rufa , hatched and reared in captivity, cannot survive in nature after their release for restocking for hunting. An attempt was made to ascertain what effect various kinds of visual experiences with man during the first 2 months of life might have on the escape-response of young individuals. It was observed that absence of visual contact with man during the 48 h after hatching causes fear of human beings in those individuals when 2 months old. Conversely, subjects which were in visual contact with man during the 48 h after hatching did not show this tendency to escape in front of him. The possible links between this finding and the phenomenon of imprinting, together with the need for new rearing techniques, are discussed.

Is foot squeezing pressure by two raptor species sufficient to subdue their prey

We quantified foot squeezing pressure exerted by Common Buzzards (Buteo buteo) and Eurasian Kestrels (Falco tinnunculus) while grasping a rodent. The birds were offered either a dead laboratory mouse, a fake mouse consisting of a laboratory mouse skin surrounding a rubber pipe connected to a pressure transducer, or a live laboratory mouse. Direct observations and necropsy of the depredated mice confirm death by suffocation from the raptors grasp. The two raptor species differed in technique of constricting the fake mouse: the buzzard relied on strong, but very brief squeezing bouts, whereas the kestrel compensated for less squeezing strength by performing constriction with prolonged duration. When observed, bites to the head were consistent with immobilizing live prey but not killing it. In contrast, squeezing by thoracic compression is sufficient to kill the prey without the need to use beak or talons.

The Nature of the Pigments in Corals and Pearls: A Contribution from Raman Spectroscopy

ABSTRACT Raman measurements at 473.1 nm on corals, both calcitic and aragonitic, and on pearls (aragonitic) were performed to elucidate the nature of the pigments, with the relative importance of methylated (carotenoids) or nonmethylated polyenes involved in the color associated with marine mineralized organisms still being a debated question. The resonance condition of the laser excitation enables the observation of overtones and combinations of four main vibrational modes of the polyenic or carotenoid pigment up to > 5000 cm−1. Raman spectroscopy proves to be a powerful tool to determine the biomineralized structure, the nature of the pigments, and the presence of artificial dyes.

Looking at a predator with the left or right eye: Asymmetry of response in lizards

Studies carried out with the common wall lizard (Podarcis muralis) revealed preferential use of the left eye during responses to predatory threat in laboratory settings and in the wild. Here we tested lizards under monocular conditions of vision, using temporary eye-patching. Lizards were facing a (simulated) predatory threat laterally, from the side of the non-patched eye. Results showed that lizards with the left eye uncovered during predatory threat used the left eye to monitor the predator, whereas lizards with the right eye uncovered nonetheless tried to use the covered left eye. Moreover, lizards frequently tried to change the eye exposition, making a body C-bend behaviour. Right-eyed lizards showed more frequent and faster C-bending responses than left-eyed lizards, trying to monitor the predator with the left eye even though it was patched. Results fit with asymmetries in spontaneous eye use observed in laboratory conditions and in the wild in this species, confirming that structures located on the right side of the brain (mainly served by the left eye) predominantly attend to predatory threat.

Antipredator behavior in lemurs: Evidence of an extinct eagle on Madagascar or something else?

Goodman (1994) related the antipredator response exhibited by two species of lemurs from southwestern Madagascar against extant birds of prey to the predatory efforts of an extinct eagle, inhabiting the same region about 4000 years ago. He argued that today’s smaller raptors, hunting young individuals perhaps only occasionally, represent marginal danger to lemurs. Nevertheless,their activity would be sufficient to impose a continuous reinforcement to a strong antipredator response. I question such an interpretation and instead suggest that extant birds of prey may indeed represent a strong threat to lemurs and that the same might not have been necessarily true for the extinct eagle. In addition, I propose four optional hypotheses, all of which encompass a marginal role for the extinct eagle.

Bird claws and bird of prey talons: Where is the difference?

The questions asked were (1) whether claws and toes of birds of prey are actually different from those of other perching birds, and, if so, (2) what parameter can describe such a difference. The structure of toes and claws of the first and third toe was then evaluated in three groups of birds: Falconiformes, Strigiformes and non‐raptorial species. One adult male per species was considered, and, among non‐raptorial birds, only species belonging to typically or partially perching families. Only one specimen per species was chosen, from museum skin bird collections. All species examined occur in the western Palearctic, according to Cramp & Simmons (1977–1994). Discriminant Function Analysis showed clear separation of the groups. In particular, the first canonical function segregated Falconiformes from Strigiformes, whereas the second separated Strigiformes from non‐raptorials. However, Falconiformes and non‐raptorials partially overlapped and were not separated. The characteristics segregating Falconiformes from Strigiformes mainly concerned claw curvature, claw length in relation to toe length, and the last phalanx shape, thin or rounded. Characters contributing to segregate Strigiformes from non‐raptorials were claw curvature in relation to their radius and the shape, thin or rounded, of both claws and last phalanxes. Results indicate that Strigiformes toes and claws only superficially resemble those of Falconiformes and the shape of claws and toes of Falconiformes are much more similar to those of non‐raptorial species than they are to those of Strigiformes.

Lateralisation in a detour test in the common wall lizard (Podarcis muralis)

Detour tests provide a reliable indicator of the presence of visual lateralisation. Previous studies on fishes and birds suggest that preferences in choosing to detour an obstacle to reach a goal are due to asymmetries of eye use. We studied detour behaviour to reach a prey in males of Podarcis muralis in order to ascertain visual laterality for a predatory task. Lizards were found to be lateralised at both individual and population levels, although only a few lizards were found to express lateralisation at the level of the individual. The preferential direction of detouring is the left route around a transparent barrier, indicating a right eye/left hemisphere use to observe the prey and confirming the results of recent work. The eye used to fixate the prey was maintained longer in the same direction the lizards subsequently chose to approach it, confirming that the preference was basically due to visual asymmetry, not to motor asymmetry. To our knowledge this is the first study of detouring conducted on sauria, demonstrating how these lizards are right eye/left hemisphere lateralised for predatory tasks at individual and population level.