NO, 5 BEHAVIOR OF THE NIGHT MONKEY — MOYNIHAN II 



very aggressive, the attacker generally pauses a few seconds, before 

 starting another slow and cautions advance, preparatory to another 

 attack leap. 



The Night Monkeys kept in captivity on Barro Colorado Island 

 generally were quite silent while attacking ; but once I heard an indi- 

 vidual "spit," like a cat, at the very instant of jabbing an opponent. 

 Hill (1960) mentions similar sounds in similar circumstances. So 

 perhaps spitting sounds are a normal part of the attack behavior of 

 Night Monkeys, at least in some populations of the species. 



Sometimes two individuals will try to attack one another simultane- 

 ously. This may lead to a brief but extremely violent wrestling match, 

 while each animal tries to bite and/or strike the other. 



All these patterns, with the possible exception of "spitting," would 

 appear to be expressions of the attack tendency alone. At least, they 

 do not include any components that are unmistakable indications of 

 any other tendency. 



Other attack reactions may be less direct. It is not uncommon to 

 see an aggressive animal leap over, or just to one side, of its oppo- 

 nent, instead of directly toward it. An aggressive animal leaping in 

 this way is less likely to bite or strike its opponent than is an animal 

 that has leapt more directly. In such cases, it would appear that the 

 attack has been "deflected," probably by some counteracting tendency. 



The tendency most likely to counteract attack during most hostile 

 encounters is undoubtedly escape. There is considerable evidence 

 than an escape tendency generally is activated to some extent, how- 

 ever slight, in all or most situations in which attack is activated. Even 

 the most aggressive animals sometimes interrupt their attack behavior, 

 by retreating briefly and/or performing displays which probably in- 

 clude an escape component. 



Mated pairs of captive animals kept in adjacent cages may become 

 engaged in vigorous disputes with one another. In such cases, it is 

 obvious that usually males try to attack males while females try to 

 attack females. Males also tend to attack more frequently, on the 

 average, than do females. 



Captive Night Monkeys seldom "redirect" (see Bastock, Morris, 

 and Moynihan, 1953) attack upon individuals other than the ones 

 provoking the attack. They certainly perform redirection attacks 

 much less frequently than do individuals of many other species of 

 Platyrrhini in similar circumstances. This seems to be due partly to 

 the fact that direct expression of their aggressiveness is seldom or 

 never impeded by any positively "friendly" gregarious tendency. Even 



