Tag Archives: Flora & Fauna

20,000 Salmon into the Sea

Salmon in California have evolved to follow the seasonal rhythms of wet and dry periods as they migrate between their natal streams and the ocean, and then back again. The fall rains that swell Lagunitas Creek and herald the return of adult salmon to Marin County also encourage young coho salmon to begin their downstream journey to the ocean. In normal years, winter is the time when many of these young salmon migrate from headwater tributaries down to lower Lagunitas Creek, where they transform into silver smolts in preparation for the ocean phase of their life cycle. These smolts wait in the lower creek until April and May before entering the ocean, just in time to take advantage of the spring plankton bloom.

Dry period yields more coho fry.

Years 2013 and 2014 have not been normal, however. Fall rains were infrequent and light, and January was the driest on record. The drought caused a significant delay in salmon spawning and resulted in a much smaller coho run than expected. The extended dry period did, ironically, seem to benefit the young salmon preparing to emigrate to the ocean. Many coho fry were unable to migrate downstream until the rain finally arrived in February, which meant that they weren’t packed together in lower Lagunitas Creek. The habitat in the lower creek can’t support very many young salmon through the winter, which appears to be one of the principal factors limiting the size of the entire coho salmon population. This year, salmon fry spent the winter spread throughout the watershed, and likely spent little time crowded in the lower watershed.

More salmon possible in 2015

The result was the largest emigration of salmon smolts yet seen in Lagunitas Creek. Biologists with the Watershed Stewards Project, the Marin Municipal Water District, the National Park Service, and the Salmon Protection and Watershed Network counted coho smolts every day between late March and early June as they migrated past traps on Lagunitas, Olema, and San Geronimo Creeks. In typical years the lower watershed doesn’t appear to be able to support more than approximately 11,000 juvenile coho salmon through the winter. This year nearly 20,000 coho smolts emigrated to the ocean. What does this mean for the future of coho salmon in Marin County? In the short term, if food is abundant in the ocean we could see 2,000 adult coho return to Lagunitas Creek in 2015 (the most in more than half a century). On the other hand, this year’s smolts were fairly small and may not survive well. Over the longer term, while we can’t recreate this year and prevent coho from migrating to the lower watershed, we can provide more habitat there.

A grant currently being considered by the California Department of Fish and Wildlife would fund the construction of five projects in lower Lagunitas Creek to expand side channels and floodplains for coho salmon winter habitat. Hopefully this grant will be funded and the projects will achieve their goals. As with the seasonal migrations of salmon, we’ll just have to wait and see.

Eric Ettlinger is an aquatic ecologist with the Marin Municipal Water District

 

Badgering my Neighbors, Part Three

Continuing the story of the Badger and its hunting strategy, we will look a little deeper into the typical digging pattern. The shallow digs surrounding the large burrows are sometimes called probe holes. Here, the badger is hunting for a gopher who is out in newly dug tunnels, shallow cul-de-sacs where the gopher is feeding.

The strategy, I think, is to trap the gopher in one of those dead ends where the badger can dig up the gopher faster than the gopher can dig to get away. With each probe dig, the badger is mapping out the gopher’s tunnel system and working his way closer to the hot-smelling, active gopher. My theory is that the badger may actually be herding the gopher into a dead end!

Rough calculations: if a grown badger eats two gophers a night, that’s a lot of gophers! And a lot of badger holes. If a successful pair of badgers produces two litters of four in an excellent year, you’ve got eight badgers consuming several hundred gophers per month! Add in the other gopher predators, the red-tailed hawks and harriers, the coyotes, foxes and bobcats, weasels and skunks, gopher snakes and rattlers, etc.; then add in the voles, mice, brush rabbits, birds, snakes, frogs and other abundant prey, and it is mind-boggling how many animals are being consumed. But that indeed is what is going on out in our fields.

Now, what about the role of the coyote in all of this badger activity? They both love to dig up gopher nests, and their holes are similar sizes. But there are several ways to tell them apart. Inland badgers primarily hunt ground squirrels and coyotes will work with the badger in the hopes of catching a squirrel using an escape hole to make an above ground dash to another burrow system. Gophers don’t escape this way however, so our local coyotes don’t partner up with badgers the same way, but they will both hunt the same gopher territories.

The difference in their digging patterns are tied to their respective morphologies. The badger, with its short legs and low-slung body, digs in at a relatively shallow angle, kicking the soil out behind itself with its partially webbed back feet, and usually the badger hole quickly begins spiraling down. It is amazing to see the speed at which they can dig, soil flying furiously out behind them as they quickly disappear into the ground. With their long claws and powerful arms, they are able to remove rocks as large as softballs, and their “throw-mound” is very large—three to four feet long or more, and is usually thrown in only one direction.

The coyote, on the other hand, digs dog-like, standing on its long back legs while reaching into the hole to dig with its front paws in a paddling digging style, and pulling the soil out with their front feet. They will often work their way around the edges of the hole, spraying the soil in all directions. They leave a much smaller (average 18 inch) throw-mound even if most of it is in one direction, because they are only digging down to the nest.

Both animals make holes that are 8 to 10 inches in diameter. But classically the badger, with its inward turned legs and flattened body, makes a horizontally flattened hole, while the coyote, with its long-legged paddling motion, will tend to make a vertically narrowed hole. But this often doesn’t hold true when the coyote circles the hole while digging. In most cases, the coyote digs much more straight down compared to the shallow ramp of the badger, and the coyote mostly goes for the nest, so it doesn’t leave the messy “probe-hole” pattern around the main digs. Finally, with its lighter-duty digging equipment, the coyote doesn’t dig out rocks much larger than a couple of inches in diameter.

So, like a rare spectacular meteor shower that you might want to get up in the middle of the night to watch, we have a rare opportunity right now to see badger holes in most of our gopher habitats. When you find one, stand back and look at the overall pattern and look for neighboring digs. When you find the dried grass balls of a dug-up nest, look closely and you can see what the gophers have been eating. And look at the side walls of the hole where you can often find grooves left by the large claws.

But always, above all, be respectful in your studies. Give the natives some space. Be careful with your own impact—my goal is to be as invisible and non-disruptive to animals as possible, even while using tracking and awareness skills to get in close amongst them.

Richard Vacha

Pt. Reyes Tracking School

Comments and feedback welcome!

Email me: rwvacha@horizoncable.com