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Posts tagged “Tamias striatus

Eastern Chipmunks Emerging & Mating

3-13-17 e. chipmunk IMG_2353

All winter long, Eastern Chipmunks have been intermittently napping and running to their underground larder to snack every week or two. As spring approaches, the timing of their emergence above ground is affected by the weather, even though their tunnels are 18” – 36” below the surface. Within the last week chipmunks have been seen above ground.  One would think they must be in a state of confusion, given the erratic weather we’ve experienced this spring.

Chipmunks waste no time once they are active.  Most adult females are in breeding condition when they emerge (as opposed to males, which are in a state of constant readiness) and mate within a week. This involves 10-30 couplings within about a 6-7 hour receptive period.  In a month or so, the results of these efforts will be born.

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Forest Floor Mystery: Pellets? Old Scat? Cache?

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Lying at the base of a large Eastern Hemlock I recently found two piles of bleached bones.  One pile consisted of mostly vertebrae; the other pile had numerous tibias, humeri and ribs.  All were the appropriate size and shape to have come from several Eastern Chipmunk skeletons – at least four or five.   How did they end up in two distinct piles?

The lack of any fur indicated that regardless of how these bones came to be here, they were deposited quite a while ago.  The lack of any partial skulls or jaw bones and the large number of bones in each pile led me to believe that these were not the remains of two pellets that had been regurgitated by resident Barred Owls. No wild owl pellet I’ve ever dissected, including the large pellets cast by Snowy and Great Gray Owls, has contained even half this many bones, and most contained at least part of a jaw bone.

If not pellets, then scat?  How likely is it that a predator could catch and consume multiple chipmunks rapidly enough so that they would end up in the same pile of scat?  One feasible explanation could be that a fox, coyote or fisher preyed on young, inexperienced chipmunks, but the bones were adult-size bones.

Perhaps these two piles are the remains of a predator’s cache – perhaps a bobcat?

The possibilities are endless as to how this chipmunk graveyard came to be.  However, none of the theories proposed here can explain the dissimilarity between the types of bones in each pile.  If any naturally curious readers have insight into this phenomenon, your thoughts are welcome!

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Determining An Eastern Chipmunk’s Gender

3-4-16  chipmunkIMG_2353Ordinarily, one can’t tell a male from a female eastern chipmunk as they look identical –but there are two times during the year when it is possible, with luck and good eyesight, to tell one from the other. One is right now, in the early spring, when chipmunks first emerge from their underground burrows. Male chipmunks appear first, followed by females one or two weeks later. The first of two breeding seasons is beginning for chipmunks.  Upon emerging, the males’ testicles descend, making the males distinguishable from the females. Their scrotal sac is covered with whitish-gray fur; the darker the fur the more mature the chipmunk is.

During their breeding season, males travel outside of their home ranges, often some distance, to locate females and check on their reproductive condition. The females chase and wrestle with the males to see who can keep up with them. When a female comes into estrus (the end of February/ beginning of March) she chooses her mate. The chosen male flicks his tail vertically and screams prior to copulation (another way to distinguish the sexes). After the first mating season, the testicles ascend until the second breeding season in middle to late summer, when the chance to determine the gender of chipmunks once again presents itself.

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Eastern Chipmunks Soon To Encounter Round the Clock Darkness and Periodic Torpor

11-6-15  eastern chipmunk IMG_0439Although Eastern Chipmunks are much in evidence during our current November heat wave, these lively rodents will soon retreat underground to their maze of interconnecting tunnels for the winter. This burrow system usually has one unobstructed entrance with the opening of other tunnels that lead to the surface plugged with leaves. A chipmunk may dig part of the burrow system using its forefeet and cheek pouches to loosen and transport soil, but the renovation of old root channels and existing burrows of other mammals is the primary method of burrow construction. The two-inch diameter tunnels are roughly 12 to 30 feet long and typically 18 to 36 inches deep. Off of these tunnels are several food galleries as well as a chamber six to ten inches in diameter which contains a nest of leaves.

Chipmunks reside in their subterranean environs from mid-November until early March – late April, with local snow depth and temperatures influencing the duration. They are not true hibernators and accumulate little body fat prior to winter. Throughout the winter chipmunks are aroused from their state of torpor every week or two and snack on their underground caches of food (up to 5,000 – 6,000 nuts per chipmunk, according to one source). During mid-winter thaws, some chipmunks may leave their burrows, even digging through several feet of snow to forage for seeds in nearby areas where the snow has melted and the forest floor is exposed.

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Eastern Chipmunks Up & Active

3-23-15  eastern chipmunk IMG_2146Eastern chipmunks typically emerge above ground in late March, at a time when most mature females are in breeding condition. It takes little time for nearby males to come courting. During their breeding period, females, for the most part, remain within their territory, whereas males explore within and outside of their territories in search of a receptive female.

Male suitors congregate on the site of a female in estrus and work out the hierarchy within the group. The top chipmunk wins the opportunity to breed with the female. During these dominance battles, the males vocalize, wave their upright tails from side to side, chase each other and fight. The dominant male then breeds with the female. She proceeds to mate anywhere from 10 to 30 times within about a six to seven-hour receptive period, not necessarily with the same male. All of this activity takes place within a week of when chipmunks come above ground, so keep your eyes peeled for those waving tails.

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Warmer Winters Threaten Hibernating & Torpid Mammals

12-6-13 eastern chipmunk IMG_2845Winter air temperatures have increased in the Northeast during the past 100 years. A study by Craig Frank of Fordham University has found that as winter temperatures heat up because of global warming, chipmunks in areas that have experienced warmer winters become less likely to hibernate in the coldest months. The research indicates that chipmunks that follow normal hibernation procedures enjoy a survival rate through winter of about 87 percent, while those that remain active because of warm winter weather are almost certain to die by spring (due to higher metabolism requiring more food). This finding could mean dire consequences for all mammals that hibernate or become dormant during winter months, as exceptionally high winter temperatures correlate positively with reduced hibernation, resulting in a lower winter survival rate for these animals.

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Eastern Chipmunks “Clucking”

10-2-13 eastern chipmunkIMG_3035Especially in the fall, and sometimes in the spring, the woods are full of “clucking” Eastern Chipmunks. It’s unusual to hear this call during the summer, but once leaves have started to fall off the trees, giving chipmunks a clearer view of the sky, the chorus begins. One chipmunk starts calling, and the message is passed on to other relatives, who join in. These vocal little rodents are warning each other of the presence of an aerial predator, perhaps a hawk or day-hunting owl. The next time you hear this distinctive alarm call, look skyward. You may well be rewarded with the sight of a raptor flying overhead.

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