A deadly balance: predator versus prey on Antelope Island
Ava Godsey, 5, and her brothers, Jordan, 10, and Josh, 7, look at a snake skin during the Sharp Teeth and Hooked Beaks: Predators of Antelope Island class at the visitors center on Antelope Island on Saturday, August 30, 2014. (BRIANA SCROGGINS/Standard-Examiner)
Antelope Island Naturalist Morgan Swenson, of Ogden, holds a replica of a bobcat skull during the Sharp Teeth and Hooked Beaks: Predators of Antelope Island class at the visitors center on Antelope Island on Saturday, August 30, 2014. (BRIANA SCROGGINS/Standard-Examiner)
Antelope Island Naturalist Morgan Swenson, of Ogden, holds a replica of a badger's skull during the Sharp Teeth and Hooked Beaks: Predators of Antelope Island class at the visitors center on Antelope Island on Saturday, August 30, 2014. (BRIANA SCROGGINS/Standard-Examiner)
ANTELOPE ISLAND — If you let your house cat outside one night and it doesn’t come back, kitty may have decided to go on a grand adventure of Utah’s great outdoors — or, you may have unwittingly provided a tasty meal for a neighboring Great Horned Owl.
“The Great Horned Owl has a very diverse diet,” said Charity Gibson, a ranger and naturalist instructor at Antelope Island State Park, during her presentation Sharp Teeth and Hooked Beaks: Predators of Antelope Island on Saturday. “He eats lots of different things: other birds of prey, rodents, gophers, rabbits, domestic cats, porcupines. Great Horned Owls are also the main predators of crows.”
Gibson started out her presentation by defining the terms predator (an animal that eats other animals) and prey (breakfast, lunch, or dinner for an animal higher up the food chain).
“I like predators,” 6-year-old Zakiah Schneider said in response before eliciting giggles from the rest of the room with, “I think I was a T-Rex in a past life.”
Gibson then introduced her audience to the snakes of Antelope Island — none of which are venomous. Gibson said the garter snake and the racer are both common to Antelope Island and approximately the same size, with the racer being slightly larger. Being similar in size also means they share a similar diet of mice, small rodents, insects and lizards.
Gibson said garter snakes are generally laid back and non-aggressive, but racer snakes can be very aggressive and visitors should not attempt to handle them.
Gibson, who has been an employee of the state Parks and Recreation Department for 10 years, recently transferred from Utah Lake State Park to Antelope Island and said she was greeted with a surprise during her first day on the job.
“One of these guys was actually in my office the first day I got here,” Gibson said, pointing to the photo of a racer projected on the screen behind her. “Just as I was saying to myself that that was a pretty cool model of a snake, it stuck its tongue out at me.”
Gibson said the largest snake on Antelope Island is the gopher snake (a.k.a. bull snake), which looks similar to a rattlesnake and can grow up to five feet long. Gopher snakes feed on rabbits, kangaroo mice, and– you guessed it — gophers.
“Some gopher snakes try to imitate rattlesnakes to scare predators,” Gibson said, adding that though gopher snakes don’t have rattles, they will shake their tails through dry leaves to imitate the sound of a rattlesnake.
Then, she shared something truly horrifying. Most people know that snakes regularly shed their skin. But, did you know a snake’s eyeballs are part of the shedding process? Gibson showed her audience the skin of a gopher snake she’d recently found near Fielding Garr Ranch — taking care to point out the two, shiny domes under which there used to be a pair of eyes.
“Snake skin doesn’t grow and stretch, so they shed it,” Gibson said. “And that includes the eyeballs. That means snakes are very vulnerable when their eyes start to shed because they can’t see very well.”
Gibson said badgers can also be found on the island.
“They’re very aggressive hunters. They’ll eat anything that burrows,” Gibson said, adding that badgers often block the exits on a given prey’s tunnel system before tunneling in after them.
Bobcats also inhabit the island and Gibson said their snack of choice is a cute, cuddly cottontail rabbit.
“They make their dens amongst rocks or in caves and eat mostly cottontail rabbits,” Gibson said, pointing to a photo of a bobcat taken just outside the island’s amphitheater. “They hunt through stealth and speed. They also eat skunks, raccoons, voles, birds and reptiles.”
Other predators on the island include the American kestrel, the bald eagle, the burrowing owl and barn owls. But, the largest predator on the island is the coyote.
“They eat just about anything; anything that’s edible. They’re scavengers,” Gibson said. “What I find really interesting about them is that they change their hunting techniques depending on what type of prey they’re trying to catch.”
Gibson said coyotes will use stealth when hunting smaller game, but will hunt in packs when taking down larger game.
“Some deer or pronghorn hunts can take anywhere from eight to 20 hours,” Gibson said, adding that when pack hunting, coyotes will chase a victim until it gives up from exhaustion.
Gibson said many people may feel sorry for the prey in the predator/prey relationship, but that predators are necessary.
“We need them to help keep prey populations in check,” Gibson said. “Can you imagine if there weren’t any predators to catch mice, how many mice would be on this island? There’s only so much food to go around on the island; only so much vegetation. The balance between predator and prey has worked for millions of years.”
Gibson said that of all the animals on the island, coyotes and bison are the only ones with no natural predators on the island.
“Coyotes are very good at self-regulating populations with alpha pairs,” Gibson said. She said there is only one alpha pair per coyote pack and the alpha pair is the only breeding pair in a pack. If a subordinate pair breeds, the alpha pair will kill the subordinate pair’s offspring. Gibson said the alpha pair will also kill their own young if the pack’s population starts to become too big.
However, Gibson said the bison population has to be managed by humans through the annual bison roundup.
“Bison were brought to the island by humans, so they have no natural predators here,” Gibson said before going on to explain how bison are chosen to be auctioned off after the roundup.
To find out more about programs at Antelope Island State Park, visit the park’s website: http://stateparks.utah.gov/park/antelope-island-state-park