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https://www.sfgate.com/local/article/san-francisco-coyote-diet-study- 20025917.php
On a brisk Saturday morning in late September, Tali Caspi stood behind an information booth she had just set up on the sandy shoreline of Crissy
Field near the East Beach parking lot. It was draped with a black
tablecloth and accentuated by a single cardboard sign.
“My PhD is on SF coyotes,” it read. “Ask me anything!”
Caspi wasn’t sure what to expect. But she certainly didn’t think she’d
spend the next three hours talking “nonstop” with over 100 San Franciscans
who lined up to speak with her about the presence of the urban apex
predators in their city and the purported risk they posed to their
children and pets.
It had been just over a month since a spate of coyote attacks on dogs had
been reported not far from where the growing crowd of locals had gathered. Earlier that summer, a coyote bit a 5-year-old girl who was attending day
camp just a few miles away in Golden Gate Park.
Some of the residents were frightened. Many of them were angry. And all of
them had questions. Was the coyote population skyrocketing? Were they developing a taste for their canine peers? And why didn’t the city
relocate the carnivores — or get rid of them entirely?
“It was intense,” Caspi remembered during a recent conversation with
SFGATE. “I think people are struggling to understand the ecology of what’s going on, and the individuality of these animals.”
For the past five years, the UC Davis PhD student has been working on a
study exploring what the native California species is actually eating, published in the scientific journal Ecosphere on Tuesday. Throughout her research, she’s heard her fair share of misconceptions about the maligned canine, but for the first time, she has the data to debunk them.
What’s on the menu
The study, completed between September 2019 and April 2022, utilizes 707
pieces of scat left behind by over a hundred coyotes across the city.
Armed with Google Maps and a fanny pack, Caspi spent countless mornings
seeking out and collecting the crucial evidence for her research in
manicured golf courses, busy neighborhoods and quiet cemeteries. Back at
the lab, Caspi and her team at UC Davis’ Mammalian Ecology and
Conservation unit ran the scat through a DNA metabarcoding process and
were stunned by what they found.
The highest overall contributor to coyote diets in San Francisco was anthropogenic, or human-origin, food, which was identified in 78% of the samples collected. The data was most frequently traced back to coyotes
dwelling in parts of the city with more manmade land cover, like asphalt
and brick. Caspi cited three hotspots in particular — Coit Tower, St.
Francis Wood and Bernal Hill — all of which have smaller ratios of green
space to dense urban landscape.
“I don’t think people realize the sheer extent of human food that is
consumed,” she said. “It surprised me.”
https://s.hdnux.com/photos/01/46/47/63/26901705/8/ratio3x2_960.webp
A chart showing the diets of coyotes throughout San Francisco.
Tali Caspi/Figure 2a of "Impervious surface cover and number of
restaurants shape diet variation in an urban carnivore"/Ecosphere
The breakdown of human food consumed by coyotes included 509 detections of chicken and 250 detections of pig, followed by 32 detections of cattle and
15 detections of salmon and other fish. The findings come with the caveat
that Caspi is unable to distinguish the original source of the food — if a sample of chicken is coming from a wayward McNugget tossed out of a car
window, scraps left in an unsecured trash can, or a whole rotisserie feast intentionally left out for the wild animals, which she once witnessed firsthand.
“There’s no way to know for certain,” she said. “But it’s a novel
behavior, and the reason why we’re focusing on it is because anthropogenic
food consumption can presumably exacerbate conflict and have other physiological consequences for the animals.”
The second most commonly eaten food group in San Francisco’s coyotes was
small mammals, which were found in 73.8% of the collected samples and
include invasive pest species such as black rats, Norway rats and house
mice, Interestingly, Caspi was able to link higher rates of consumption
of these pest species to territories with more restaurants, specifically
the 1-kilometer areas surrounding Coit Tower and North Beach as well as
Corona Heights and the bordering Castro, Haight and Mission District neighborhoods. She argued that it demonstrates the “enormous power” people
have to manipulate their surroundings in ways that shape individual
animals’ foraging behaviors. On one hand, businesses and residences in the
area could be more diligent about how they dispose of waste, but on the
other, they could look at the ecological service as a benefit.
“If people don’t want coyotes in certain areas, then we need to make sure
that we don’t have attractants there for them to use,” she said. “Because
they are using them. And they are using them massively.”
The rest of the coyote diet breakdown included a 23.6% occurrence of
birds, primarily pigeons and ducks, a 22.8% occurrence of medium-sized
mammals such as raccoons and skunks, and less than a 1% occurrence of
herptiles like slender salamanders and bullfrogs. In the marine mammal category, Caspi found traces of a lone sea lion and a fin whale that
washed up on Fort Funston in 2021. But also eye-opening to her were the individual preferences that varied from animal to animal, as was the case
with one coyote that had a particular affinity for skunks.
“We can only hypothesize why,” she said with a chuckle. “Maybe it truly
did not have a good sense of smell, or some other kind of olfactory dysfunction. But it’s not so crazy to think about. Let’s say you and I are going to an ice cream shop — we’re going to pick different flavors because
we have different preferences. Why would we assume that other animals
don’t as well?”
The same theory extends to the coyote that went after the small dogs in
the Presidio last year. Notably, Caspi’s study is unable to turn up
results for domestic canines because the marker she uses to sequence DNA
is the same across all canid species. In terms of other pets, she found
just 32 detections of domestic cats, which made up 4.5% of all samples,
and two domestic guinea pigs, which she thinks may have been let loose in Golden Gate Park.
It’s true that several components may factor into the dietary decisions
San Francisco’s coyotes are making, including the hunting and foraging strategies they learn from their parents, as well as the success rate of
their own experiences with new sources of prey. While Caspi’s study shows family groups tend to have similar diets, the individual favoring dogs in
the Presidio territory was part of a group that ate a greater percentage
of small mammals like voles and pocket gophers. This lends evidence to her belief that the choices of one individual do not reflect the entire
population.
“It wasn’t that all of a sudden all of the coyotes in San Francisco were attacking small dogs. There was one,” she said. “I don’t know why or how
it adopted that strategy, but I think the role of research is to try to
figure out how these individual differences develop so we can target them before they cause havoc.”
Coyotes in the city
With a population of over 870,000 people, San Francisco is one of the most densely populated cities in the U.S., and also famously has more dogs than children. Sightings of coyotes are not uncommon, and the city regularly enforces closures around denning areas when pupping season is underway. Confrontations with pets can happen, but many of the hundreds of calls
made to San Francisco Animal Care and Control are unsubstantiated reports, spokesperson Deb Campbell told SFGATE in September. She referred to one instance last summer when reports of a coyote with a Pomeranian in its
mouth in Bernal Heights turned out to be a mom carrying her pups.
The last few months have been “fairly quiet” in terms of human-coyote disturbances, Campbell told SFGATE on Monday, with the late fall and
winter season tending to be less active for the agency, but staff are
still receiving reports of coyotes rifling through garbage and of people feeding the animals.
A myth Caspi hears all too often that could be driving the calls is that
San Francisco’s coyote population, which currently sits at around 100
according to Animal Care and Control’s estimates, is rapidly increasing.
Not only is that biologically impossible, she said, but it’s also more reflective of human perception than anything else. “There’s been an
explosion of coverage, and that makes people more aware,” she said.
Caspi also attributes the pandemic to a change in human behavior as people began to spend more time outdoors and in the city’s parks.
“Just because a lot more people are paying attention and seeing coyotes
doesn’t mean there are more coyotes,” she said. “They could be seeing the
same individuals.”
As people and coyotes continue to overlap, Caspi also often hears the
question of whether the animals belong in the city or if they should be
pushed out. It’s an important reminder that they predate European
settlement in this part of California and were “here first,” she said.
Though coyotes were locally extirpated in the 1920s as a result of killing competitions, bounties and poisoning, new laws were passed that banned
state and federal agencies from incentivizing such practices, and they
began to make their way back to the city in 2002.
The opportunistic creatures quickly reacclimated and are here to stay. Not
only is it illegal to relocate coyotes, per California law, but it’s also ineffective: The animals will try to return to their home territory and
either create conflict with other coyotes or die on the journey. If that happens, coyotes can respond to changes in their populations by producing larger litters, Caspi said.
Yet, she feels San Franciscans are resistant to viewing their city as a
broader ecosystem where all of the organisms within it have important
roles to play. Coyotes help control nuisance species like rodents, reduce disease transmission, boost bird populations by reducing the numbers of
other predators, and provide other services like distributing seeds for a
wide variety of plants. The best thing people can do, Caspi said, is
accept the reality of their presence and learn how to coexist with them.
She also pointed out that Crissy Field, in particular, is part of National
Park Service land and the Golden Gate National Recreation Area, which
lists “preserve local biodiversity” among its priorities for wildlife management.
“You wouldn’t have somebody go to [Yellowstone] and get their dog gored by
a bison and be like ‘What the heck?’” she said. “My bias is how wonderful
that we have these natural places and access to biodiversity in our city.
How amazing that San Francisco is a city where all of its residents live
within a couple blocks of a public park. But that talking point doesn’t
always work as well.”
An urban jungle
Aside from one other 2022 study published on the diets of urban coyotes in
New York City, Caspi’s paper is the only one of its kind to utilize DNA metabarcoding to understand what coyotes are eating at population, family
group and individual levels. As part of her ongoing research, she plans to compare the diets of coyotes in San Francisco to those in non-urban environments by using stable isotope analysis to detect diet composition
from coyote whiskers based on their distinct chemical signatures. She’s
also studying how stress levels and thyroid hormones respond to coyote
diets. Both are expected to be published in her dissertation when she
graduates later this year.
“I think there’s a lot to learn from this species and how much they’ve
done to adjust,” she said. “The reality is they live here and we can’t
change that. I hope it encourages people, in some ways, to find something
to admire about these animals.”
When Caspi set up her information booth last September, something peculiar caught her eye just beyond the swarm of people asking her questions. A man
was running by with his AirPods in, while his small off-leash dog trailed
along behind him. They passed one of the signs warning of coyotes in the
area and disappeared into the fog.
“I also hope people realize that a lot of conflict is preventable,” she
said. “And they have the tools to stop it.”
--
November 5, 2024 - Congratulations President Donald Trump. We look
forward to America being great again.
The disease known as Kamala Harris has been effectively treated and
eradicated.
We live in a time where intelligent people are being silenced so that
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Durham Report: The FBI has an integrity problem. It has none.
Thank you for cleaning up the disaster of the 2008-2017 Obama / Biden
fiasco, President Trump.
Under Barack Obama's leadership, the United States of America became the
The World According To Garp. Obama sold out heterosexuals for Hollywood
queer liberal democrat donors.
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