Aardvarks to Zebu: Post 2

Every so often we choose a challenging rehabilitation question and poll two to four experts on the topic.  This time, we chose “Explain the difference between an imprinted or socialized animal, or are they the same thing?” and asked it of a behavioral scientist who works at an education and behavioral research facility with captive canids.  If you have your own burning question, email me at director@theiwrc.org.  The question just might find its way into a future post!

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Aardvarks to Zebu:

Wildlife Rehabilitation Quandaries and Conundrums

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Explain the difference between an imprinted or socialized animal, or are they the same thing?

Pat Goodman – Wolf Park

ABSTRACT:  Imprinting and Socialization are closely connected behavioral events.  Imprinting occurs during a limited period of time, typically for a short period after an animal is born or hatched.  It has a profound effect on the young animal as it matures, determining to what species the infant will show social behavior, and sometimes determining from what species the animal chooses its mates.  Knowledge about imprinting is necessary in captive breeding programs if the animals so reared are to be able to choose and mate normally with their own species rather than choosing individuals of the same species as their foster parents.

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While there will be variation depending on the species in question, socializing an animal means to rear, or interact with it in such a way that it can use its repertoire of social signals with other animals.  One of the prerequisites for socialization to a species other than its own is a reduced flight distance from that species.   Usually an animal is socialized to its own kind by interacting with its parent or parents, and other members of its social group.  As it matures, its experience and skills in social interaction expand to include others besides its parents and its siblings or other age mates.  Sometimes an animal acquires the ability to respond to the social signals of animals not of its own species, typically through either rearing by foster parents of a different species, or, later in life, repeated exposure and opportunity for non-damaging interactions with another species.

Often socialization to species other than its own is best begun when the animal is very young.  Socialization to humans later in life can be more stressful and risky for the animal and human involved, and the range of the social repertoire that the animal shows to humans may be only a fraction of what it would show to its own kind.  Wolf Park’s bison, for example, are somewhat socialized to humans through repeated contact paired with special food such as apple slices or sweet feed, and the opening of gates to greener pastures.  We do not make attempts to socialize them extensively.  They do a little bit of greeting occasionally, sometimes solicit food, and sometimes warn or threaten us.  Their social signaling to us is limited compared to the social signaling between us and the wolves.

Imprinting is not, itself, socialization, but it may determine what a young animal becomes socialized to.  Imprinting takes place during “critical periods” in the development of an infant animal.  Often this period starts very shortly after it is born or hatched.   During this time, the infant learns very quickly and very thoroughly to recognize a blueprint for a parental figure.    Once this sensitive period is over, socialization to other species, while theoretically still possible, tends to be more labor intensive, less complete, or even impossible given the limitation of resources in the real world – time and skilled caregivers.  It also tends to be less effective, less enduring, and may involve more hazards to the animal being socialized and the one doing the socializing.  Successful socialization to an animal of a different species, or even its own species, once the sensitive period for imprinting is past, may involve isolating the subject from its own species, and making it dependant on a member of another species for all its social contacts.

In some species this early imprinting also affects mate choice later on, if, in addition to recognizing its parent, the young animal learns to prefer an animal matching its parent’s blueprint as a mate when it matures sexually.  Typically it does not imprint on its individual parent as a future mate, but will prefer an animal of the same species as its parent.  If it has a foster parent not of its own species, it may reject mates of its own kind when it is an adult, and court members of the same species as its foster parents.  Some newly hatched birds can even imprint on inanimate models as parental figures.

In precocial species, which can run around shortly after birth, the infants often show a readiness to follow something that moves in their immediate vicinity.  An infant can develop a strong interest in an object and then be less interested in other objects to imprint on.  Often this attachment can be enhanced by food rewards.   Normally such reinforcement is provided by the mother, who may also reward infants with warmth and pleasant social touch.

The length of this sensitive period varies according to species, and to some extent, on the particular circumstances.  According to the Oxford Companion to Animal Behavior (David McFarland, editor, p. 303) “Domestic chicks kept in groups cease to follow moving objects 3 days after hatching, but chicks reared in isolation remain responsive for much longer.  In natural conditions the young birds would become imprinted upon one another; chicks and ducklings tend to stay close together, even in the absence of a parent.”

As young animals develop, they often begin to explore, and at some point many of them show signs of neophobia, fear of novel things.  This fear can interfere with the young animals’ abilities to form attachments to other animals, including humans.  At Wolf Park we discovered that we must take wolf pups away from their mother and start hand-rearing them at 10 to 14 days of age.  It is not enough to leave them with a wolf mother who will permit trusted humans to visit daily and handle the pups.  The mother-reared pups will show some shortened flight distance from us as they mature but they will not show much of their social repertoire to us and they will not solicit many affiliative interactions; rather, they tend to stay out of reach.  If, however, we take the pups away from the mother, but keep the litter together, so that they get near constant contact with their own litter mates for wolf –to-wolf socialization, and give them about 2000 human hours of social contact, which takes more than one human, starting from their removal from their mother at 10 to 14 days old, until they are 16 weeks old, we have wolves who will be able to show the full repertoire of social behavior to their own kind and almost their full repertoire of social behavior to humans as well.

Historically, researchers studying the biology of behavior used imprinting to do experiments that required cross fostering, producing young that were thoroughly socialized to a species not their own.  Once these young animals were mature they were willing to mate with members of their foster species, and, in turn their offspring often demonstrated which behaviors were inborn, and which behaviors were learned during individual development.  Such research was done a lot with birds, which often imprint on their foster parents’ species as future mates.  Such sexual imprinting seems to happen less often with mammals, according to the Oxford Companion to Animal Behavior, but it can occur.  Wolf Park once received a wolf pup rejected by his mother, and also he was the only survivor of his litter.  Reared in a children’s zoo until he was five months old he had plenty of exposure to humans, but no experience of canines until he came to Wolf Park.  I do not recall him ever showing courtship to other wolves, though several of our females found him attractive and courted him.  He preferred to court humans, and vigorously rebuffed female wolves.

To sum up, imprinting is a type of learning restricted to certain periods very early in the development of animals.  During these sensitive, or critical, periods, an animal’s preferences for social companions, and mates may be determined and it may be difficult, or impossible to change them later in life.  In some species, food preferences, and preferences for a certain kind of habitat may also be established very early in life.  Animals may be able to imprint on more than just one species.  Konrad Lorenz and his students were able to “infiltrate” their goose flocks and study the birds’ behavior at very close quarters by imprinting goslings on humans as well as on geese.

At Wolf Park, whose founder, Dr. Erich Klinghammer, regards Lorenz as a friend and mentor, we do something similar with wolves.  Since our wolves are not candidates for release in the wild, and so need not be fearful of humans for their own safety, this type of rearing facilitates our husbandry procedures throughout their lives.  It makes additional environmental enrichment opportunities available, since some of our routine maintenance can be a social occasion in which the wolves participate willingly.  It reduces the stress of being in captivity and contained in fairly close proximity to the visiting public.  Routine care, and even some emergency medical care can be accomplished without tranquilizer guns, nets, etc.   If a wolf is driven from its pack, or if it outlives its pack members and we cannot provide it with another compatible wolf as a companion, humans may be that wolf’s only source of friendly social interaction, especially for social touching.

Imprinting does not guarantee that a wolf will always be safe and easy to handle.  It does result in a wolf that is typically open to life – long learning about, and, we hope, improvement of its social skills with humans.  This openness is achieved and maintained by carefully monitoring our interaction history with wolves, use of some classical and operant conditioning, and attempting to understand their physical perceptions and emotional states, plus their individual developmental and history of personal experience with humans and their environment.