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CDFW Pilot Study Establishing Foundation for Enhanced Study of Porcupines

CDFW Pilot Study Establishing Foundation for Enhanced Study of Porcupines

Four men standing next to each other with snow on the ground and trees in the background
Porcupine1: NRVP participants Greg Moore, Mike Maulhardt, Charles Brown and Ben Smith volunteered to service and maintain porcupine stations at Red Lake Wildlife Area.

Trail cam image of a porcupine between two upright posts at night


Trail cam image of a porcupine on ground amongst trees at night


Trail cam image of two porcupines near tree at night


Trail cam image of a porcupine on top of rock behind two upright posts at night

Not to put too fine a point on it, but studying California’s porcupines hasn’t traditionally been a high priority for CDFW.

Wildlife research funding is limited, especially for non-game species, and species listed as threatened or endangered are typically given top priority. That means that scientists sometimes need to be creative – and frugal – in their efforts to survey and manage non-listed, non-game species.

Stacy Anderson, a CDFW senior environmental scientist specialist based in Rancho Cordova, recently conducted a pilot project that does just that.

Anderson developed an interest in the North American porcupine (Erethizon dorsatum) in 2017, after acknowledging that anecdotal evidence seems to indicate their numbers are on the decline.

Porcupines have historically inhabited diverse habitats including Humboldt County, along the Sacramento River, in the Coast Ranges, the Klamath Mountains, the southern Cascades, the Modoc Plateau and the Sierra Nevada. But in her conversations with unit biologists and wildlife officers in some of these areas, Anderson took note that many were reporting a substantial decrease in the number of calls from residents whose property – typically wood structures such as decks and outhouses – had been damaged by porcupines in recent decades. Informal surveys of veterinarians across the state also indicated a decline in the number of pet owners seeking quill removal from their pets.

Perhaps most telling, CDFW’s Sierra Nevada monitoring project, which has studied portions of the Sierra for the past nine years, has documented only seven porcupine sightings out of 750 stations surveyed via trail camera.

“We are worried about them because we don’t have a lot of sightings,” Anderson said. They live in low densities and they have only have one baby per year, so they don’t repopulate quickly.”

Recognizing the need to gather more information, Anderson and Evan King, another CDFW environmental scientist, launched a pilot effort last year to improve surveillance of porcupine, with a long-term goal of determining distribution and population numbers.

Anderson and King were inspired by the work of Uldis Roze, a researcher who has long studied porcupines in the Catskills of New York by using wood soaked in salt brine as a porcupine attractant. His research indicates that porcupines show a strong seasonality of salt use, which peaks in April through May and August through September. Because porcupines’ diet of plant matter is generally low in sodium (salt), they seek out other dietary sources of sodium to maintain normal levels in their bodies.

Anderson and King theorized that brined wood could be effective in attracting California porcupines, too. A plan was made to soak stakes made from 2x2s in a sodium brine to monitor activity. In theory, tooth scrapings on the wood could also be identified to species.

“It’s not a full-blown study – it’s just a way to test a plan of action that can maybe be used in a study later,” Anderson explained. “We don’t want to waste valuable resources on untested methodology, so this is a way to find out first if the methodology is going to work. It’s a low-cost, high yield approach.”

Twenty-three stations were set up for the 2017 pilot project, which was conducted from April to October. Members of CDFW’s Natural Resources Volunteer Program, who support departmental operations, supplied much of the labor, and the study costs were kept low. Expenses added up to less than $100, including salt for brining and wood. Trail cameras borrowed from other researchers were utilized to help monitor the stations.

Researchers were pleased to learn that the porcupines took to their efforts with a grain of salt (so to speak). They determined that brined-wood monitoring is more effective than traditional bait or game-trail monitoring, at least in the study area in northern Sierra and along the Sacramento River. Preliminary results indicate that the brined wood appeared to lure porcupines into the area of a camera station -- although most did not approach the wood and fewer still left a distinctive chew mark on the brined wood. But the trail cameras provided clear, useful photographs.

“We still have unanswered questions about this technique that will need to be addressed before we can consider it a success,” Anderson said. “However, our pilot efforts are promising.”

CDFW is seeking additional funding through state wildlife grants and collaborative efforts with other researchers and agencies to gain a better understanding of the North American porcupine’s status. Anderson plans to continue refining the methodology of her study, along with other survey techniques including habitat surveys, feeding signs, tree girdling, scat searches and the use of detection dogs.

Anderson also encourages members of the public to help CDFW’s efforts by reporting detections of live or “roadkill” porcupines.

CDFW Photos. Top Photo: Porcupine photo by CDFW Warden Chad Alexander.


Saving the Burrowing Owls

Saving the Burrowing Owls

Burrowing Owl being held while one hand slightly extends owl's wing

Burrowing Owl in hand

A dwindling population of a tiny owl in Southern California has a chance at a comeback, thanks to a collaborative effort by scientists from CDFW, the San Diego Zoo’s Institute for Conservation Research (ICR), Caltrans and the U.S. Fish and Wildlife Service.

The Western burrowing owl (Athene cunicularia hypugaea) is currently listed as a Species of Special Concern, and nongame scientists have long been concerned about their viability and survival. Breeding populations have especially declined in the central and southern coastal areas, due in large part to a combination of habitat loss and eradication of the ground squirrels that dig out the burrows where the owls make their nests. In San Diego County specifically, the once-widespread population has been reduced to a single breeding node in the Otay Mesa region, just north of the Mexico border.

Two groups in particular have been monitoring these owls carefully, in an effort to help. Biologists from Zoo’s ICR have spent seven years assessing owl population status and productivity, including assessing the feasibility and effectiveness of artificial burrows, refining techniques to help the ground squirrels thrive and disperse into new areas and developing a system of identifying potential new locations where the owls might thrive. Much of ICR’s owl research has been conducted at Brown Field, a small municipal airport near the border within the City of San Diego, and on an adjacent property owned by Caltrans.

Meanwhile, about 10 miles from the Brown Field study site, CDFW scientists have spent a decade working to create more suitable burrowing owl habitat at Rancho Jamul Ecological Reserve (RJER). Efforts there included installation of artificial burrows and mowing the tall grass to foster a low-growing grassland suitable for burrowing owls and ground squirrels. Despite their best efforts, CDFW scientists studying the Rancho Jamul site have experienced many years of disappointment -- although wintering owls have shown up every year, none have stayed and attempted to breed on the property. But conditions have been improving over the last four years, thanks to the implementation of a grazing program that reduced dense thatches of old grasses and expanded areas of open ground. As habitat changed at Rancho Jamul, CDFW scientists observed more squirrel burrows, and the conditions seemed just about right for the owls.

This spring, an approved development project at Brown Field began to take shape – and it became evident that the timing for an owl translocation project was ripe at last. Thanks to efforts by Caltrans, which incorporated burrowing owl habitat restoration as part of their mitigation effort for a nearby highway, CDFW staff believed the owl population to be strong enough to support a translocation effort. Also the spring season, just prior to egg-laying, is likely the optimum time to move the animals. After looking at many options, scientists decided to try to move five pairs of breeding owls to RJER in the hopes that they would establish a new population and thrive.

The full conservation team – which included CDFW, the U.S. Fish and Wildlife Service, the City of San Diego, Metro Air Park, Schaefer Ecological Solutions and the San Diego Zoo – was on board and ready to move the owls. In March 2018, the team caught five pairs and moved them to hacking cages at RJER. The owls lived in the cages for about one month to give them time to acclimate to their new surroundings. By the time the cages were removed, each female had laid at least one egg in the artificial burrow chamber.

CDFW Environmental Scientist Dave Mayer has worked on this project for years and is anxious to see efforts at RJER finally pay off. The presence of the eggs, he said, was thrilling to see. “More owls, and at diverse locations, is what it will take to conserve this species in San Diego County. This first step was a long time coming, but I have all my fingers crossed that it’s going to work.”

This successful multi-agency partnership will continue long past the actual translocation day. Scientists banded the owls and fitted some with radio transmitters. ICR staff will monitor the owls themselves, while CDFW staff will monitor the grassland and the grazing program, and perform inspections and repairs of the artificial burrows twice a year. After five years, CDFW will perform regular monitoring of the owls, the habitat and associated grazing practices, and the general status of the ground squirrel population.

Mayer is proud of the work achieved so far in this unusual project. “We built a better mousetrap, with the Zoo’s help,” he says. 

General information about California’s bird species of special concern can be found on the CDFW website, along with the link opens in new windowspecies account (PDF) for the burrowing owl and information about Rancho Jamul Ecological Reserve.

The San Diego Zoo has also issued a link opens in new windownews release with more details about the burrowing owl translocation project.

All photos © San Diego Zoo Global, all rights reserved

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