Granite Basin denizens

visiting the world of marmots and spotted sandpipers

A long, lazy lunch, which we enjoyed while sprawled on a huge boulder in the noontime sun: we basked like lizards—or, more appropriately for our locale, like marmots.

Soon thereafter, we were whistled at—by a pair of baby marmots that had just recently begun to emerge from the den where they were born. These toddlers tried very hard to sound the alarm about the ‘monsters’ tramping along the creek, but their whistles sounded very raspy and feeble. That didn’t deter them, however, and they shrilled every few seconds until we were well past their rock.

It seems to take a while for youngsters to learn how often to ‘cry wolf’. Adult marmots would probably not have gotten quite so excited at the sight of two-footed monsters traipsing by. Interestingly, baby beavers behave much the same way, tail-slapping over and over again at something strange, often ignored by their parents, until they learn to tailor their alarms to the circumstances.

hoary-marmot-young-of-the-year-sept-5
A young hoary marmot

The scientific name of our hoary marmot is Marmota caligata. The second name refers to boots, because the marmots’ black feet reminded some taxonomist of that footgear. Farther south, hoary marmots typically inhabit high elevations, with other marmot species at lower altitudes, but in our area, these marmots range from sea level to the alpine zone.

These marmots have a very flexible mating system. Some mate in pairs, or social monogamy; a study in south-central Alaska suggested that this was the common arrangement there. Others are polygynous, two or more females socially bonded to a male. Sometimes an extra male resides on the periphery of a mated male’s territory. Regardless of the social arrangement, however, there is reportedly a lively scene of extracurricular activity. Males go gallivanting over the hillsides, looking for receptive females. And they find them: many litters have been shown to have multiple fathers. So perhaps the two we saw were just half sibs.

Gallivanting males are most common in big patches of suitable habitat, where several colonies of marmots are neighbors. Small habitat patches may only support one family group and opportunities for gallivanting are fewer. Males reportedly behave more parentally when gallivanting is not an option; they guard their offspring more assiduously and even play with them.

Hoary marmots typically mature disperse from their natal territory to find their own place in the world when two years old. Mature females, age 3 or more, can produce a litter every year if food is very abundant but often skip a year or two if food is scarce. Mating occurs in spring, soon after the adults emerge from hibernation. Gestation lasts about four weeks and the pups are weaned after roughly four more weeks. Litters usually consist of about three pups, but pup mortality can be high, especially during winter. Litter size and frequency of reproduction varies with the social mating arrangements: monogamously mated females produce larger litters more often than bigamously or trigamously mated females, which are more likely to skip a year—and whose males do more gallivanting in the females’ off-years!

I heard but failed to see a spotted sandpiper near the pool at the top of the falls at the basin entrance. Spotties are found there virtually every year. They usually nest on gravel bars and upper beach fringes, and the basin provides several gravel bars.

Spotted sandpiper females arrive first on the breeding ground and claim a territory. Males arrive later and set up their own territories inside those of females. Some females mate monogamously, and both parents may care for the eggs; this mating arrangement is more common among younger females. Older females are commonly polyandrous: a female often mates with two or even three males in succession. She lays a clutch of four eggs for Number 1 and leaves him to do all the incubation and chick-tending, while she goes on to Number 2. If there is no Number 3, a female may help Number 2 care for the brood.

spotted-sandpiper-by-bob-armstrong
Photo by Bob Armstrong

Some polyandrous females bond with males within her original territory. Others search widely for a second mate. It turns out these females keep track of their neighbors and they know which territories previously have been successful in producing chicks. And to the males on those territories go the females to find a sire for their second broods. In this case, it seems to pay to be a nosy neighbor!

The plot thickens still further! Those second males may indeed perform all their parental duties and also may be helped by the female if it is her last brood of the season. But second males are not necessarily the fathers of the chicks. In some cases the female stores sperm of Number 1, which becomes the father of at least some chicks in the second brood. In effect, Number 2 has been cuckolded by the first male and ends up caring for another male’s chicks.

 

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