Ethology and veterinary practice: Specialists and generalists
Friday, December 01, 2017
Ethologists who study wild animal behavior use the terms generalist and specialist to describe two different survival strategies. Generalists can thrive in a wide range of environmental conditions and on a varied diet. Specialists, on the other hand, only can thrive in limited environmental conditions and have specific dietary needs.
Each of these orientations includes the necessary physiological and behavioral adaptations to support them, and each has its benefits and costs.
The upside of being a generalist eater is obvious. The more varied the diet, the less time it takes to locate something to eat.
On the downside, natural food sources such as growing plants and prey species possess mechanisms to protect themselves from being eaten, and generalists may lack the targeted skills necessary to overcome these efficiently. If it takes more energy to incapacitate, eat and digest a food source than the energy gained from it, the generalist will be worse off than eating nothing at all.
Specialists face the opposite situation. Everything about their anatomy, physiology and behavior enables them to excel at dispatching and digesting their specialized food sources compared to their generalist neighbors.
However, it may take them longer to locate their primary — and sometimes only — food source. Worse, if that food source disappears because of natural disaster, habitat destruction or the effects of climate change, the specialist's chance of survival will plummet. For example, the fate of the specialist panda hinges on that of several species of bamboo; as the eucalyptus goes, so goes the koala.
But "specialist" and "generalist," like "social" and "solitary," are terms those in the behavioral sciences use to describe statistically average predictive behaviors within a certain species. Whether a specific member of that species may display these behaviors depends on multiple genetic, epigenetic and environmental factors.
Nowhere is this more obvious than in companion animals whose behaviors further have been influenced by the ongoing effects of domestication.
Traditionally, cats are described as true carnivores and predators, and dogs as omnivores. However, in veterinary practice it's possible to see cats and dogs who disprove this description. How far they deviate from the norm of their free-roaming canine and feline ancestors depends on how far removed they are from those roots.
Let's look at some feline examples.
Butch, a short-haired mackerel tabby comes from a long line of predatory cats who formed relationships with humans. Were he so inclined, he could trace his roots to mousers who arrived on colonial ships then disappeared into the woods to fend for themselves.
Butch lives with his owner on 50 acres of woodlands. He exits through his cat door after sunset to hunt rodents in the woods and outbuildings, and reappears before dawn the next morning and sleeps most of the day. When bad weather keeps him indoors, he hunts in the basement or attic of his owner's home.
On average, only about a third of Butch's hunting attempts succeed. Two-thirds of the time, his prey detect some stimulus that causes the animal to bolt before Butch can pounce. Other times, Butch aborts the hunt due to insufficient stimulation from the prey — e.g., sound motion, odor, etc. — to stimulate his appetite.
Butch's hunting strategy gains him three benefits other than a meal.
First, he's as familiar with not eating as he is with eating. This is a crucial survival skill for any animal, but especially for a free-roaming one. Second, the stimulus-dependency nature of his predatory strategy protects him from eating weakened prey that might jeopardize his own health if consumed. And third, it endears him to his human companion who appreciates Butch's skill at keeping her home and outbuildings rodent-free.
Even though Butch has access quality cat food, rodents are his food of choice. As the feline-rodent predator-prey relationship has evolved in his area over the years, rodent physiology has evolved to maximally digest and utilize the nutrients in rodent dietary sources in that area. Simultaneously, feline physiology has evolved to gain the maximum nutritional benefits from the rodents.
Is it any wonder that those who attempt to turn cats like Butch into apartment-dwellers may find their pets far more interested in stimulus-rich human food than some inert cat food in a bowl?
BijouBlanc is a white Persian who, his owner boasts, can trace his purebred heritage back to those first purebred show animals in the late 1800s. You needn't observe him for long to discover he's an environmental specialist.
Unlike Butch, his specialized environment is limited to the confines of his owner's cozy condo. His premeal ritual consists of uttering a polite meow, silently watching his owner rush to prepare his gourmet diet and gently warm it in the microwave, and sitting patiently in his special chair while she ties his bib so he doesn't soil his fur while he eats.
But although Bijou puffed up and yowled in fear the only time he saw a mouse, he's not that far removed from his predatory heritage as his owner would like to believe.
A survey of the cat's toys reveals that all those she describes as his favorites trigger a predatory response. She drags feathers or ribbons and he engages in the same stalk, pounce, pinion and bite sequence Butch does. "Bijou and I both love playing these games!" she says.
When his owner isn't home and Bijou is in the mood for play, anything that moves in the condominium is fair game. Sometimes this works out better for him than others.
On the upside, Bijou didn't kill the spider plant; he only stalked, pounced on it and shredded its dangling "baby spiders" with his claws. On the downside, the owner's delicate silk scarves hanging in the closet are history.
Then, there was the day he discovered he could track the letter carrier's approach through the neighborhood, then race to the door and position himself ready to pounce on and shred the mail as it magically flew at him through the brass mail slot in the door. To him, this too was a wonderful game. His owner did not agree.
And finally, we have Bruno whose ability to evade all the people and vehicles that invade the area behind "his" restaurant attests to his specialist's knowledge of his environment. At the same time, though, his diet is generalized.
Following a banquet, he feasts on scraps of steak, mashed potatoes, gravy and cake. The next day, he eats limp French fries, veggie burgers and coleslaw. The day after, the restaurant was closed for a holiday, and he ate whatever he could find on the ground around the empty garbage cans.
Three quite different cats displaying quite different orientations toward their environments and food supply. Although we may perceive some of these as more acceptable than others, I can't help but marvel at how the basic specialist and generalist concepts may play out in one of our most numerous domestic animal species.
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