Rubbing its dorsal gland against 
a rock face, this peccary is scent- 
marking a boundary site of its 
herd's home range. Neighboring 
herds seldom mark over each 
other's scent deposits. 
in the lead, followed in single file by 
the juveniles, then the rest of the 
adults. If the disturbance is more im- 
mediate (as when the observer blun- 
ders into the midst of a herd), the 
animals tend to scatter in all directions 
in an every-peccary-for-itself manner. 
This set of strategies makes sense. If 
defense or organized retreat is pos- 
sible, it is carried out. If the danger 
is so large and imminent that defense 
would be futile, the herd’s scattering 
may tend to confuse a predator. It 
also would tend to draw attention away 
from the helpless juveniles, which in 
these situations seek some kind of 
cover and remain motionless. Herds 
quickly regroup after a disturbance, 
individuals using the low grunt to lo- 
cate one another. 
A third form of mutual assistance 
is cooperative nursing. Unlike females 
in most ungulate species, peccary fe- 
males will allow young other than their 
own to nurse. Juveniles approach from 
the rear and suckle while the female 
stands. Females do not turn around 
to check the identity of these young, 
and it seems that most young are able 
to nurse from most females that have 
milk. On several occasions in herds 
that had many new young, there was 
a snapping, jostling horde of hungry 
young at the rear end of one female. 
There were obvious injustices — with 
larger young pushing smaller ones 
aside — but the nursing females con- 
tinued to munch cactus complacently, 
as if the storms behind them did not 
exist. Milk production in mammals 
is an energetically expensive business, 
and females of most species usually 
make sure that they give milk only 
to their own young. In many ungulates, 
females will not tolerate an alien ju- 
venile in their vicinity while they are 
nursing. I thus found it striking that 
peccary females seem to distribute 
milk indiscriminately. 
Peccaries are also unusual mam- 
mals in that males do not compete 
actively for mating rights. When a 
female is in estrus, there may be a 
slight increase in aggressive behavior, 
but more often than not, pairs court 
and mate with other males quite close 
by. On one occasion I saw a female 
mate with one male, then turn and 
court and mate with another while 
the first stood idly by. I found it cur- 
ious that males seem to give up in- 
dividual reproductive success. The 
most likely explanation is that the 
males in a herd are so closely related 
to each other that for any individual 
the difference in real reproductive suc- 
cess between a female producing his 
offspring or the offspring of another 
male is so slight that it is not worth 
fighting about. It is not known if in- 
breeding reveals deleterious recessive 
genes in peccaries or if there are social 
mechanisms that preclude matings be- 
tween very closely related individuals. 
The low level of competition be- 
tween males is also reflected by the 
lack of sexual dimorphism in pec- 
caries. Males and females are equal 
in body size, and both sexes have large, 
sharp canine teeth. In other species 
that have mating systems in which 
males fight for access to females, 
males are usually much larger than 
females and tend to have large, con- 
spicuous fighting and display struc- 
tures, such as the horns and antlers 
in many other ungulates. The lack of 
sexual dimorphism in peccaries sug- 
gests to me that the species has had 
a substantial evolutionary history of 
reduced male-male competition. 
The collared peccary is thus, by 
many measures, a highly social beast. 
The animals in a herd are cohesive 
and possess two specialized ways of 
maintaining close contact (the mutual 
rub and the low grunt). There is co- 
operative feeding, mutual tolerance of 
young by all adults, regular play that 
involves all herd members, cooperative 
nursing, and reduced male-male com- 
petition. The species is close to one 
extreme of the spectrum of mamma- 
lian sociality and was indeed appro- 
priate for my study of behavioral de- 
velopment. 
The development of behavior and 
the nature of early experience in pec- 
caries is another story in itself. The 
gist of what I found is that in de- 
velopment, as in adult social behavior, 
peccaries are different from most 
other mammals. In other highly social 
species, juveniles interact amicably 
with each other and in this way prob- 
ably form the bonds that draw them 
together as adults. Peccary juveniles 
barely interact with each other for 
the first seven months of life and when 
they do interact, it is likely to be in 
a fight over access to food or a fe- 
male’s teat. Yet these juveniles even- 
tually grow up to become amicable, 
cohesive, and cooperative adults. 
Adult tolerance of juveniles is prob- 
ably vital in this species, and juveniles 
seem to be brought into the social 
group via their interactions with 
adults, not their interactions with each 
other. There are intricacies in this pro- 
cess that I will try to sort out in future 
field seasons. □ 
66 
