Gray Fox Report for July 2015

Gray Fox Report for July 2015

Respectfully Submitted by William C. Leikam
Founder of the Urban Wildlife Research Project (UWRP)
Date Submitted: August 5, 2015


In June’s email I opened, “With the loss of the litter around the water treatment plant, with Little One in seclusion and none of the other females in the region having a litter [that I know of], the only female to have a single pup seems to be Dark Eyes.” During the month of July, I had to correct that. It wasn’t Dark Eyes who had the single pup. Instead it was Cute and her mate the alpha male Dark who have the single pup. Dark Eyes may have a litter but if so, she is keeping it hidden and even at night for I have not seen any of her pups on my cameras. As we enter August, I grow more and more skeptical that she has a litter at all.

  • Last year at this time of year we had 27 adults and pups combined. This year we have a total of 10 adults and as far as I know one pup. That is a dramatic decline in the number of foxes at the baylands. Last year with the high number of foxes in the area, we saw a serious overpopulation problem. Dens were nearly side-by-side especially in the overflow channel and that resulted in both adults and pups fighting. I would propose that last year’s gray fox population may have had an effect on this year’s decline.
  • How could that be? Dr. Robert L. Crabtree writes, “It cannot be over emphasized how powerfully coyote populations compensate for population reductions. Such density dependent responses … are common in mammals and present in all territorial populations at or near habitat saturation.” — Dr. Robert L. Crabtree, President and Founder Yellowstone Ecological Research Center, Bozeman, MT, Research Associate Professor, University of Montana, Missoula, MT. [pdf]
  • The inverse of this is also true. Might it be that the foxes have reduced the number of young because of the overpopulation of last year? It could be reasonably seen as being so for Dr. Crabtree states that this fluctuation is common in mammals. It appears as if the Palo Alto Baylands was near habitat saturation, for under normal conditions, a gray fox “family” needs approximately one square mile of land/territory to raise its young. Around the San Francisco Bay it is not possible for any of the foxes to have such a luxurious expanse. As a result, their territories overlap considerably.


  • July has been rather routine. In each of the three dens that I have been monitoring, in the early part of July the foxes fed on Italian Buckthorn berries, Elderberries, and other fruits as seen in their scats. This is typical fare for them. Now, here in late July at least two of the dens have taken to eating flesh once again. In the case of the pair with the pup, some video clips show an adult bringing in what appeared to be a duck. Across the marsh at the other side of the range, the adult male Gray caught and killed a fully fledged young Canada Goose. (Gray is a master hunter.) It is presently that time of year when the foxes crossover between protein and vegetable/fruits.
  • Somewhere around the area there is a food bowl filled with kibble. Both Gray and his mate Mama Bold have defecated when I have been present and both have been feeding on kibble in addition to goose. Mama Bold is constipated and I think most likely from eating the dry dog/cat food. This is the first time I’ve seen that happen with the gray foxes.
  • Finally, back along the overflow channel behind the Palo Alto city maintenance yard or service center, as based on scats, a coyote passed through. It was during this time too, that Cute took to barking both in the evenings and sometimes in the early morning. A gray fox will only bark when it is in distress and is warning the other foxes in the area that something is seriously amiss. A coyote is deadly to gray foxes because coyotes prey on them. Within the past week and a half, everything has settled down. Cute no longer barks as she once did and I have not seen any fresh coyote scat along the channel.

Within the permit that allows the Urban Wildlife Research Project to conduct its study of the behavior of the gray fox, the objectives covered are:

Monitoring of urban gray fox denning sites in Palo Alto Baylands.

This is being accomplished during the period when the gray foxes use a den site. It is one of the prime locations for gathering most of the behavioral data on the litter and on adults alike.

Assessment of status and population trends of Bayland’s urban gray foxes.

See above – As of June 2015, it appears as though the number of gray foxes at the baylands has declined considerably. This brings up the question: As with coyotes that can regulate the number of pups born in a region, might also gray foxes do the same?

Identification of habitat features that promote the presence of urban gray foxes.

As stated in last month’s gray fox report, there is a need to undertake some work to increase the habitat features required by the gray foxes in an area where a road was built that borders the saltwater channel. I asked construction supervisor Frank Muzzi about this and he felt that the old growth Coyote Bush would grow back within the coming year and therefore accomplish the same goal. UPDATE – After considering this and talking with people who know how to restore habitats, we need to assess what kinds of plants would grow best along the edge of the saltwater channel and alongside the marsh. The Alkaline Saltbush is one but there are probably others as well. We need to grow a permanent habitat that contains the corridors and plant it as soon as possible. We’ll keep an eye on this as this is a critical link between the southern region of the baylands and the northern region.
Assessment of reproductive success and identification of factors that promote successful reproduction.
NEW INFORMATION Last month I wrote that gray fox reproduction at the baylands appears to be holding steady with an average of 3.3 pups developing to maturity during the 2013 and 2014 seasons. As noted above, the 2015 season has fewer pups than in years past. Solution? Open up the pinch-point along Matadero Creek by developing thickets that link one area to another.

Identification and assessment of possible dispersal travel routes.

Presently there can only be guesses as to dispersal travel routes. We intend to make this important question much more concrete when we attain our collaring/take/capture permit from the Department of Fish & Wildlife.

UPDATE – As of July 27th, the Urban Wildlife Research Project has a fully licensed and permitted biologist experienced in handling mammals willing to capture and collar a number of adult and juvenile gray foxes.

As of the present, we have 11 gray foxes including the pup and an unknown number of foxes that do not normally make a live appearance.

Update for the Urban Wildlife Research Project – Greg Kerekes and Bill Leikam

As an update on events occurring with the Urban Wildlife Research Project:

  1. We are working to develop an integrated, seamless animal corridor from Redwood City, south along the bay into the Alviso area and then north to the southern edge of the Oakland Airport. This work is already underway. We have submitted an application to post two trail cameras on the Google Campus in Permanente Creek. The permit was granted by the Santa Clara Valley Water District and we are presently monitoring wildlife traffic crossing the creek.
  2. A new documentary has been released, titled The Gray Foxes of Silicon Valley. [video]
  3. On April 10, the Palo Alto Weekly ran a feature article about our work with the gray foxes. [article]
  4. On July 26 and 27, I presented my talk on the gray foxes atSafari West near Santa Rosa, California. It was a humbling experience. On Sunday night I presented to the public. Adults and children of all ages attended. During the Q/A part, more kids asked questions than did adults; the inverse of what normally takes place. I highly recommend Safari West. It is an amazing place. Their purpose is to breed African wildlife, including birds. [video]
  5. On August 8 and 9, my business partner Greg Kerekes will be making a presentation at Safari West on the plight of the burrowing owl.

Until next month, I hope that your endeavors are productive and rewarding. Take care.