The reason behind the rattle: Naturalist explains the biology, behaviour of rattlesnakes

While many try to avoid rattlesnakes — or any snakes — at all costs, Calgary-based naturalist Brian Keating actually went searching for some while near the Red Deer River badlands last week.

As is always the case, Keating wanted to study the creatures, not disturb them, but that didn't stop what looked like a pregnant female rattlesnake from protesting when he found her, he said on The Homestretch.

He was camping at a friend's ranch, and he went looking under some materials where irrigation piping and heavy boards were piled up.

"She let us know immediately she didn't approve of our presence," he said. 

With a combination of powerful venom, thermal radar and enhanced senses, rattlesnakes are amazing predators aptly suited for keeping rodent populations in check, Keating said.

In the case of humans, fatalities are rare.

"In fact, there is not one confirmed record of a person in Alberta ever dying of a snake bite," he said.

Snakes typically bite only if they feel threatened or provoked, according to Keating, and in a large portion of cases where bites are involved, the victims saw the snake but did not move out of the way. 

Of the three snakes Keating observed last week, two immediately retreated when discovered.

They'll try to warn you of their presence, too, Keating said, by using a rattle formed by interlocked segments of keratin — the same material our fingernails are made of.

The segments are fitted loosely and click against one another when they move. When the snake erects its tail and vibrates its muscles, the segments collide with each other to produce the rattling sound. 

Snakes aren't actually born with the rattles. It's something Keating found out while working with the Canadian Wildlife Service in Saskatchewan.

"I actually watched 21 baby rattlesnakes being born … they are indeed born 'live,' hatching out of their egg inside the female," he said, adding baby snakes are called "snakelets."

"At birth, a 'pre-button' is present at the tip of [the] tail; replaced by the 'button' several days later when [the] first skin is shed. No sound can be made until the second segment is added, and another rattle segment is added each time the snake sheds."

Snakes shed their skin several times a year, depending on food supply and growth rate.

They travel with their rattles held up to protect them from damage, but their day-to-day activities in the wild still cause them to regularly break off end segments, Keating said.

"Because of this, the age is not related to the number of rattles on the tail. They rarely can keep more than 10 to 12 rings before some layers start to break off."

Rattlesnake venom

Snake venom works incredibly well on their intended prey.

The venom is hemotoxic, which means it destroys tissue and disrupts blood clotting. It contains a mixture of up to 15 enzymes, and it's designed to immobilize and disable prey while breaking down tissue for digestion.

The older the snake, the more potent the venom, Keating said, with larger snakes able to store large volumes of it. Venom is very stable, lasting for years in storage.

The predators will lie in wait and strike with their fangs, eating gophers, mice, voles and other small animals, which makes them important for rodent management.

"If the bitten prey moves away before dying, the snake follows its scent," Keating said.

"Once the prey is incapacitated, the snake ingests it head first.… They have powerful gastric juices, digesting even bone."

One of Keating's favourite facts: Rattlesnakes are "pit vipers," and they can detect thermal radiation emitted by warm-blooded organisms.

"These cues are transmitted to the brain and are used to create thermal maps of the snake's environment, allowing the snake to visualize an area in low levels of light," he said.

They also have eyes designed for nocturnal life and a keen sense of smell.

To keep your distance, Keating said he advises hikers to be particularly careful when climbing over logs or boulders or when walking near outcroppings and ledges, as the snakes like to lie in the sun. 

If you do see one, and you hear that classic rattle, Keating has an idea of what the snake might be saying: "'I'm here, step on me and you WILL be sorry!"

For more fascinating stories about Alberta's wildlife from naturalist Brian Keating, visit his website and check out these stories: