This is the second article in a series about animal behavior: Part I | Part II | Part III | Part IV

Fear plays such a crucial survival function in all animals — including humans that the physiological and behavioral changes associated with it are deeply rooted. Equally deeply rooted is the ability of many animals to detect fear-related changes in humans. Not so deeply rooted in some of us is the ability to detect fear-related changes in them.

Consequently, the first step to dealing with fear involves acknowledging its existence and the role it plays in the survival of all living beings. And that means recognizing the different forms it takes.

Humans and animals typically respond to threats in one of four ways. In order of their energy demands from least to most, these are the freeze, flee, tend/befriend and fight responses. How each manifests is a function of the individual's confidence and, as always, the context in which the perceived frightening event occurs.

Animals will try to use the response that requires the least amount of energy and enables them to gain the maximum amount of physiological and behavioral stability in that environment. But if the threat persists, they may move on to another approach that requires more.

The freeze fear response

Preliminary research suggests there is a freeze/pause that precedes all four fear responses. This split-second freeze may function as a moment of choice if one believes animals capable of cognition. As far as what choice, ethological evidence indicates that two general forms exist for each fear response: one is driven by panic and the other results in a viable survival strategy.

In general, animals driven by panic have fully dilated pupils regardless of the amount of light in the environment. It's the conscious or subconscious awareness of this that often leads people to describe these animals as deranged.

In general, animals making more deliberate responses will have normal to smaller pupil size, depending on the kind of visual acuity the response demands. Here again there are exceptions, such as concurrent ophthalmic issues, that should remind clinicians of the value getting a comprehensive physical and behavioral history before making any judgments.

I mention the pause because veterinarians and staff members who interact with aggressive dogs may see or just sense this pause prior to a canine fear-fight response. It occurs right before the aggressive dog shifts his weight to the rear legs to prepare to lunge. Consequently, the complete sequence is freeze-shift-lunge-bite.

However, often this pause is perceived only as part of the fear fight response and as a sign rather than a possible opportunity to abort any following display. When humans experience this, it's often accompanied by an intake of air. I suspect the same happens in animals because processing fear-related data and acting on it require more oxygen.

While the freeze-pause represents a period of relatively high mental activity, the actual freeze response represents a state of mental withdrawal. Animals that use the most deeply entrenched freeze fear response will remain so still that any potential predators either won't notice them or, if they do, will assume the frozen animal is dead. (Although some animal predators will eat carrion, many will not.)

Opossums "playing dead" are common examples of this. Even in suburbia, chipmunks and other rodents who sense cats or other predators nearby may assume this position. If there is no wind to carry the prey's scent and the predator doesn't get close enough to pick up the scent, the prey will survive. Some in-and-out pet or feral cats who find themselves being preyed upon also will use this strategy.

Similarly, when a threatening dog approaches or lunges, some (usually) young children instinctively will freeze and shut their eyes. While some may suffer facial bruising where the dog grabbed them to signal rank, they avoid the deep puncture wounds and lacerations that occur when the child or others respond more actively to the dog's presence. This awareness underlies the "stand like a tree or lie like a log" dog- bite safety programs for kids.

Narcolepsy in dogs, horses and other domestic species may represent another adaption of the freeze fear response. In the video below, the overwhelmed animal loses consciousness for a period of time. It's possible that a less acute and more muted form of this response is the immobility of medically or behaviorally depressed animals.

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Intermittent or chronic denial may represent the mildest form of the freeze response for those unable to withdraw completely from the perceived threat. Instead, they refuse to acknowledge the threat's presence. Some animals may ignore certain animals or people in their territory completely or certain events rather than risk confrontation for some reason. This includes mentally withdrawing during routine veterinary examinations.

Unlike the above more calculated responses that attempt to make the fearful animal less noticeable in some way, freeze responses driven by panic do the opposite. These individuals tremble, drool and may vomit, urinate, defecate or empty their anal glands as they huddle in one spot and refuse to move.

Such a response would soon attract predators in the wild. But for the dog or cat or (especially young) wild mammal of any species who perceives humans as predators, this could confer a survival advantage if it caused people to take pity on these animals instead of harming or killing them.

Similarly, all the involuntary activity associated with behaviorally-induced seizures that would leave wild animals vulnerable to predation might provide a way for domestic animals in what they consider overwhelming environments to mentally escape long enough regroup. It also may cause people in the animal's environment to make stress-relieving changes.

Most certainly, it's important to remember that panicked animals who respond in these ways aren't faking either their fear or any physical symptoms. Their physical and emotional pain is real and may develop into something more serious if left unaddressed or, worse, punished.

Despite the differences between the more calculated and panic-driven freeze responses, all represent attempts to escape the threat by mentally and physically withdrawing in some way. The next article will explore two more fear responses that may complicate animals', practitioners' and clients' lives.