O. G. Dely szerk.: Vertebrata Hungarica 21. (Budapest, 1982)
Ananjeva, N.B. ; Orlov, N.L.: Feeding behaviour of snakes 25-32. o.
arrived snake starts trailing the stricken prey. All the snakes become restless and begin moving about, some attempting to intercept the prey at the sight of engulfment by the hunting snake. They then start actual hunting and feeding. Such stimulation of feeding activity due coactlon effects Is particularly characteristic for mobile Colubridae and for all Vlperidae, Crotalidae (Agkistrodon, Trlmeresurus; Bltls; Colube r, Corooella, Elaphe, Lampropeltl3, Natrix, Spalerosophls ). It is most commc» In batrachophages; the abruptly lunges at the prey serve as a strong stimulus for their conspecifics ( Cyclagres. Ptya s. N erodia, X en od on ). We have observed this facilitation of feeding behaviour in Boidae (Boa, Chondropython, Corallu s, Liasls, Python) , In small entomophages (juvenis Colube r, Eireni s, Viper a ) and saurophages with characteristic abrupt movements ( Col ube r, Psammophis, Telescopu s). Pursuit movements in these situations have a marked signal function. According to our data, social facilitation and imitation effect is maximum in the group of frog-eaters. The hunting snakes begin grabbing rapidly moving objects and even one another. Occasionally accidents occur and the snakes, with their mouths wide open, Ingest pieces of the substrate that smell of the food Item (Cyclagres glgas, Elaphe rufodorsat a, Elaphe quadrlvlrgat a, Natrix teaselata, Ptyas mucosu s, Rhabdophls tlgrlna ). Imitation and facilitation of feeding are sometimes elicited by certain snake species in interspecifics. However, the effect depends on specialization in feeding: the closer the specialization, the more marked the effect. Concrete movements, I.e. "locomotor" hunting, appear to be indices of the above specialization. For example, Elaphe rufodorsat a falls to responds when the green python, Chondropython viridi s , lunges at frogs and subsequently slowly constricts the latter. E. rufodorsat a does show the response if a ccnspeciflc or some species of the genus Natri x are hunting. This may reflect the fact that the first stages of hunting and prey retention in Chondropython viridi s and Elaphe rufodorsat a are markedly different, In E. rufodorsat a and Natrix-species are basically the same. The difference affects the later stages: E. rufodorsata strangles the prey before Ingestion, while Natri x Ingests It alive. Experiments support the idea that feeding arousal In snakes is elicited as a response to specific movements by other snakes and not merely as a response to the smell of the prey. When two glass containers are placed close to the another, each with a specimen of Rhabdophls tigrlna but only one with a frog, hunting snake will stimulate other snake which will show all the signs of feeding arousal (rapid tongue flicks, prey searching, specific body movements, active motion). An Inhibiting effect of snakes in the group c» the trophic activity of the another can also be noted. This situation occurs when dominant specimens supress the activity of weaker individuals. Bigger Cyclagres giga s of one age group supress feeding activity of smaller animals. Neck flattening and violent lunges at the prey performed by big snakes would frighten frog-hunting individuals of smaller size, the latter would take refuge and not resume feeding for a long time. The patterns of prey detection and pursuit All snakes are predators, the common feature of their trophic behaviour Is that they hunt for living animals and In the case of successful hunting swallow the prey whole. However, cases of consumption of dead animals have been recorded (SHILOV 1956, PATTEN & BANTA 1980). We have frequently observed In terraria consumption by most diverse snakes (Boidae, Colubridae, Viperidae, Elapidae) of killed rodents, brids, fishes and frogs. Moreover, there is a practice in the Zoo to food snakes of mixtures. The patterns of prey detection and pursuit, the sequence and measure in the use of analyzing organs, the food Items themselves allow to divide snakes Into behavioural sets (DITMARS 1912, WIEDEMANN 1931). The general outline of hunting in most snakes species appear to be as follows: 1. The animal either actively searches for prey or lies in ambush. 2. The animal, while In adequate motivation state, receives initial information of the proximity of prey (soil tremor-an impulse to the initiation of the Jacobson organ, visual signal-an impulse to the Initiation of the Jacobson organ, thermoreceptor perception of the item -an Impulse to the initiation of the Jacobson organ). 3. Rapid tongue flicking fallow Issuing in prey search and pursuit. Many authors report progressive frequency of tongue flicks upon Introduction of food items Into the medium (CARR & GREGORY 1976, WILLIAMS & BRISBIN 1978, DUNBAR 1979, GOVE 1979). However, the above responses of the toogue as analyzing organ Is actually seen In any situations: fright, reconnoiterlng, enemy encounter, intraspecific Interactions, hunting, search
