A Mammal Big Day in California

On 14 April 2013, my wife Marta and I unexpectedly had a mammal “big day” in California. We left our home in Angwin (Napa Valley) at 3:30 am to drop off a visiting friend, Bixis Colina, at the airport in Sacramento. A few hundred meters from home a GRAY FOX trotted across the road. Within the next half hour a VIRGINIA OPOSSUM waddled along the road, a BLACK-TAILED JACKRABBIT hopped onto the road and a RACCOON hustled across the road as we sped through Pope Valley and Chiles Valley. Later, when a BOBCAT (my lucky 13th!) dashed across the highway near Lake Berryessa, I realized we were going to have a mammal big day! I’d had many bird big days (up to 198 species in Washington state), but never a mammal big day. Soon we saw a few MULE DEER beside the highway.

While returning from the airport after sunrise, I stopped at several places along Putah Creek to search for River Otters, where I had seen them before. Unfortunately I didn’t have any luck with the otters, but I enjoyed rock climbing on some huge boulders while Marta implored me not to fall. And then I spotted a tiny black-and-white dot moving on a distant hill across the river, whipped out the big camera, and photographed a STRIPED SKUNK! We also saw a few WESTERN GRAY SQUIRRELS in the trees and when we visited a picnic area at Lake Berryessa we found a CALIFORNIA GROUND SQUIRREL.


A distant Striped Skunk photographed through a 400 mm lens.

We were both recovering from colds and had planned to relax at home after returning from the airport, but after taking a long nap (we were really sleepy!) and eating lunch, we decided to have a romantic date on the coast. At Bodega Bay we saw several CALIFORNIA SEA LIONS. It was super windy so Marta didn’t join me when I hiked out to a point to search for other pinnipeds on a tiny offshore rock. With my binoculars I tried to pick out a Steller’s Sea Lion among the California Sea Lions on the distant rock, and took some photos with a 400 mm lens; I think I can make out at least one in my photos, but I’m not certain so I’m not counting it. Then we sped to Goat Rock State Beach, where we saw a few dozen HARBOR SEALS, including an adorable white pup.

At several wetlands along the coast I searched for River Otter, including a pond where I had seen them once previously, but failed to find any. Disappointed but not surprised, we drove home. Alas, I had to pee, so I stopped beside the road high above the Russian River. A moment before returning to the car, I magically spotted through the Redwood trees a lone RIVER OTTER swimming downstream! I dashed back to the car and managed to show it to Marta, who thought I was joking. It was my best pee stop ever! Just before dark we arrived at the campus of Pacific Union College, where we live and work, and spotted several WESTERN PIPISTRELLES (tiny bats) fluttering above the sewage ponds.

Our final tally was a lucky 13 species on Saturday the 13th (luckily not Friday!), including my 13th Bobcat. All were free-ranging native species found within Napa, Yolo and Solano Counties of northern California.

To put our big day into perspective, I did an online search for previous mammal big days but found very few reports. The world record appears to be 42 species, seen on 29 May 2004 in Tanzania by Charles Foley (see “A Mammal Big Day,” published in Birding 37:128-130, 2005).

In North America, the highest one-day tally I could find was 17 species, reported from Marin County, California, by the late Rich Stallcup, but no date or list of species was provided (www.prbo.org/obs_cms/index.php?module=browse&browse_issue_num=154&browse_article_num=212&chooseIssue=1).

In late September 2011, Brian and Eileen Keelan saw 14 species, including three during a whale-watching trip, in Monterey County, central California; an additional two species were captured in traps (public.keelan.warpmail.net/chr11.pdf), but as Charles Foley reasoned in his article cited above, only free-ranging native species should be counted due to restrictions in some parts of the world on trapping.

After I posted a short summary of our big day on a birding listserve for the northern San Francisco Bay area, a few others replied that they had seen more species of mammals in a day. Peter Pyle reported doing informal mammal big days when returning from the Farallon Islands, and once tallied 17 species (18 if the introduced House Mouse is included), which ties Rich Stallcup’s record, but he could not remember the day or year, which occurred during the late 1990s or early 2000s. Alan Wight reported that his Point Reyes Bird Observatory Birdathon team, the Sonoma Gray Jays, had been keeping track of their mammal sightings while searching for birds since 2005, and had recorded up to 16 species (17 if the introduced Wild Boar is included) on 25 September 2010.

Considering the tremendous efforts of birders to establish big day records throughout North America, which have been compiled for decades by the American Birding Association, surprisingly little effort has been made to establish a mammal big day record. Based on the information that I have found, the North American mammal big day record for native species appears to be a modest 17 species, set independently by Richard Stallcup and Peter Pyle. However, it is quite possible that somebody else has observed more. A more serious effort combining marine and terrestrial mammals in California could potentially push the list much higher. It is high time for somebody to up the ante!

Floyd E. Hayes
Department of Biology
Pacific Union College
Angwin, California, USA


  • Curtis Hart

    13 is a pretty good number for North America, especially with a Bobcat and an Otter.

    I had a 12 species day in the fall of ’11 near Kingsville, Texas. I saw a few unusual species at work and then road cruised for the evening. I should have had at least 2 more though. Kevin Smith and I had a 14 species day starting in Organ Pipe NP and finishing at Pima Ranch. I believe 2 of those were unidentified, but obviously different size classes of bats. Without even trying I happened to see 12 species on a random summer day in MI. I probably also saw a bat that night, but I wasn’t interested in them at that point. I easily could have walked out to the barn to see the Big Browns that roost there. I think I also had some good days at Kenai Fjords NP in Alaska, but I don’t have records of those.

    From what I’ve seen, the record will be set with early morning road cruising to Monterey Bay, a whale watch, and then heading out to the Carrizo Plain.

  • Curtis Hart

    Looking through my records again, the Organ Pipe/Pima Ranch day was 15 species.

  • Curtis Hart

    Looking through my records again, the Organ Pipe/Pima Ranch day was 15 species, no bats

  • vdinets

    Curtis: I was just about to write more or less the same thing about Monterey… although I don’t think many people would be up for driving to Carrizo after a day of whalewatching 🙂

  • white1985

    My European record is 11 mammal species in a day and I’ve reached that number four or five times so far (once in Bialowieza and all other times in Belgium). Although the species of that record number 11 always vary (sometimes with, sometimes without bats and small rodents) it just doesn’t seem to work to see more than 11 species in a day of normal mammal watching. I guess with a specifically designed route it must be possible to see up to 15-20 species in a day in Belgium – during winter, when the bats are hibernating, maybe even more.

  • Jon Hall

    I think I saw at least 12 around Portal in 24 hours without trying to go for diversity (plus several more in traps). With better planning there you could see several more I think.

  • John Fox

    Curtis and Vladimir- maybe I’m just slow today but what land mammals would you be expecting on the way to Monterrey? I’ve never done a Monterrey pelagic, maybe I’ll try it if y’all set up the route!

    I was thinking a So Cal pelagic and Carrizo, I think we had 7 marine mammals out of Santa Barbara.

    • vdinets

      On a good day in August, you can expect 5-6 (sometimes up to 12) marine mammals on Monterey ww trip, plus harbor seals, sea otters and CA sea lions in the harbor, western grey and CA ground squirrels in city parks, plus N elephant seal, CA vole, Botta’s pocket gopher and brush rabbit at Ano Nuevo. After that you can go to, for example, Pinnacles, or Little Panoche Road, or Cone Peak trail, and add some rodents, raccoon and whatever else comes by; Pinnacles also have Townsend’s big-eared bats in caves.

  • south bay wildlife

    Another idea:
    South Bay:
    With a very early start, Early Morning Road cruising Mt Hamilton/Henry Coe SP Entrance Road (E Dunne Ave): good chances for Bobcat, Coyote, Tule Elk, Black Tailed Deer, Desert Cottontail, Black Tailed Jackrabbit, Gray Fox, W Gray Squirrel, CA Ground Squirrel, Wild Pig, Striped Skunk and at Henry Coe main campground early morning: Raccoon, Coyote, Striped Skunk.
    Mid-day Pelagic from Monterey: 5 or 6 marine mammals + Sea Otter, Harbor Seal, CA Sea Lion
    Afternoon cruising to Panoche Valley & Ltl Panoche Rd followed by night driving: good chances for Heermans k-rat and Giant K-rat, Coyote, Striped Skunk, Raccoon, Wild Pig, Black Tailed Deer, Big Eared K-rat (ssp of D. venustus I believe – in chaparral in hills), SJ Kit Fox, SJ Antelope Squirrel, Dusky Footed Woodrat (in hills) and decent chances for American Badger (one could detour to Pinnacles NP along the way and see Dusky Footed Woodrat and Townsend’s Big Eared Bat)

  • Farnboro John

    I did 17 in a day in England on 17 June 2006, at Fowlmere in Cambridgeshire for most of the day and then in my home area in the evening. The exact list was: Fowlmere – Rabbit, Weasel, Reeves’ Muntjac, Common Shrew, Water Shrew, Brown Rat, Field Vole, Wood Mouse, Fallow Deer, Brown Hare; Locally – Bank Vole, Badger, Common Pipistrelle, Noctule Bat, Serotine Bat, Roe Deer, Red Fox.

    Doing it again now I would expect to get most of the above, definitely to add Soprano Pipistrelle and maybe Yellow-necked Mouse and American Mink. I might start at dawn at Thetford for Otter but couldn’t spend long there.

    Double figures is fairly easy but to get a big list you have to be pretty sure of nailing a bunch of bats and rodents and that really requires local knowledge.

    Mammal big days are an interesting concept but I would expect someone in say Kruger to wipe the floor with the lists quoted so far.


  • vdinets

    For a world record I would suggest South Luangwa in Zambia or maybe Ngorongoro/Seronera combo… Unless you count heard-only species, in which case a night of cruising along Alto Manu with a bat detector could be a good idea.

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