Olivia Weissblum PO ’14 was walking to class in early September when she noticed a baby squirrel in the middle of the sidewalk that did not seem quite right.
“It was slowly walking away and had round blotchy fur patches on it,” Weissblum said. “Another baby squirrel climbed onto me, and I saw that it was also injured. I could tell that they weren’t going to make it, so I wrapped them up in my T-shirt and took them to the biology department, where I was told that they were poisoned and was directed to the veterinarian.”
Weissblum had not come across an anomalous occurrence at the 5Cs: Both Pomona College and Pitzer College use rodenticides to control their ground squirrel populations.
Pomona began using rodenticide in 1990, placing the poison in the Wash area east of the Pomona-Pitzer track, where the most squirrels live. In 2012, however, the college stopped using any rodenticides.
we tried not to bait to see if we had gained enough control over the
population, to see if the ground squirrels were no longer there,” said Kevin Quanstrom, Assistant Director of Grounds and Housekeeping at Pomona. “But after
about a year the population exploded.”
Neither Pomona’s Facilities and Campus Services department nor
the Los Angeles County Agriculture Department, the group that monitors
squirrel populations for Pomona and supervises its use of rodenticides, recorded
data on squirrel populations, but both groups noticed a resurgence in squirrel
numbers after just one year and agreed that the reimplementation of rodenticides was necessary.
However, the two squirrels Weissblum found were tree squirrels. Weissblum provided TSL with pictures of the two squirrels, which were tan and had bushy tails.
“Ground squirrels are the brown ones with dark stripes on their backs that you see on the ground,” Quanstrom said. “Their tails are short and thin … The tan ones with the big bushy tails that you see in the trees around Marston are the tree squirrels. We aren’t targeting them.”
No data about the efficacy of rodenticide in targeting ground squirrels as opposed to tree squirrels currently exist.
Pitzer College employs several different methods to control its ground squirrel population, including poisons and sticky trap pads, according to Arboretum Manager Joe Clements.
use bait stations for squirrels and rats,” Clements said. “It’s a bad poison in there; I realize
that. But if we had the plague here, the [Los Angeles] health department would shut the
school down. We don’t want to use poison, but we have to. If there were an
alternative, we would use it, though.”
“The ground squirrels carry fleas, and fleas can carry
diseases, like the plague and others like Rocky Mountain Spotted Fever and
chiggers, so they are a health threat on campus,” Quanstrom said.
None of the other Claremont Colleges use rodenticides.
“We’ll instead put a slurry in their holes so that they can’t come back and reuse them, in hopes that that might push them away,” he added. “We just have no desire to exterminate them.”
Claremont McKenna College does not use rodenticides, according to Jose Huezo, CMC’s Associate Director of Facilities and Campus Services. Maria Anderson, an administrative assistant for the Scripps College Maintenance Department, noted that although Scripps has an exterminator that comes every week to look for rats and other pests, the exterminator does not target ground squirrels.
Quanstrom said that Pomona puts the rodenticide diphacinone, a poison that harms red blood cells with effects much like those of rattlesnake venom, in edible grains. The poison has anti-coagulant properties that prevent blood clotting and disrupt organ functioning, leading to death several days after ingesting the product.
Some hemotoxins are illegal in California, according to the California Department of Fish and Wildlife (CDFW), due to their high toxicity toward large mammals. Diphacinone has a low enough toxicity that it is legal in California, however, as long as it is not left in open fields where it can be consumed in bulk. Pomona complies with this requirement.
“If it’s scattered over the ground, as it’s done elsewhere, then birds can eat it; other animals can eat it,” Quanstrom said. “Ours is subterranean. There’s a lid on top and it’s bolted down. There are two-inch pipe outlets that come out of the ground big enough for squirrels to climb in. It looks just like the den of a ground squirrel.”
Weissblum said, “I’m just kind of against the pointless killing of animals in general. I just don’t understand why these squirrels are a problem. I don’t get why Pomona is trying to get rid of them.”
According to the City of Claremont Municipal Code section 6.12.170, the poisoning of ground squirrels does not violate any humane rights, which have only been granted to canines.
“Claremont authorities would only step in
to prevent rodent extermination if locals complained,” said Justin Barber, Community Improvement Officer for the city of Claremont. “However, we haven’t
received any complaints about people putting out poisons to kill off squirrels
in at least 30 years.”
The Inland Valley Humane Society (IVHS) handles all issues of animal
rights for the city of Claremont, adding their own regulations to Claremont’s
provisions. Sylvia Lemus, an IVHS investigator, said that
they do not handle issues regarding squirrels.
“Rodents fall under a different management protocol than most
mammals,” Lemus said. “If poison is proven to be a threat to mammals that fall under our
protection, like cats or dogs, then protocol such as warning signs around the
poison must be put up. However, matters just relating
to rodents are handled by pest management.”
Damage to animals up the food chain is another concern surrounding
rodenticides. According to the CDFW, diphacinone is one of the weaker hemotoxins, and poses only a small risk
to predators of ground squirrels such as raccoons and coyotes.
A report released by the U.S. Department of Agriculture (USDA)
Wildlife Services indicates that while the risk is minimal and the chance of
death is almost nonexistent, there are detectable effects in birds
and land mammals that consume rodents with diphacinone in their systems.
Nina Karnovsly, assistant professor of biology at Pomona and an expert in animal ecology and
vertebrate biology, agrees with USDA’s analysis.
has the potential to impact species other than the target species,” Karnovsky said. “I believe that diphacinone is not as bad as some of the
others, but it’s still not great. It is true that many pesticides move up the
food chain and impact top predators such as birds of prey, coyotes, and bobcats.”
Because rodents poisoned with hemotoxins die several days after
consumption, it is difficult to predict where poisoned squirrels might
go. An undetermined number of squirrels with diphacinone in their
systems may be available for the local coyote population to consume, which may negatively impact the health of the coyotes.
Bob Robinson, Vice President of Pomona’s Facilities and Campus Services, acknowledged this
“There’s always that potential that something, somebody, somewhere
is going to get into [the rodenticide] and it’s going to cause some ripple
effect,” Robinson said. “I’m not going to say it’s completely harmless and nothing is going to
happen. Nobody can give you a guarantee like that.”
“However, we take every precaution that we possibly can,” he added. “It’s
supervised by a government agency, so we’re following the guidelines for