Small squir­rels, shrink­ing habi­tat

Rappahannock News - - NATURE - PAM OWEN [email protected]

In learn­ing about a species, of­ten start down what ap­pears to be a sim­ple path leading to a mun­dane life, only to be drawn into a much more com­plex world with fas­ci­nat­ing in­ter­con­nec­tions. I be­gan such a jour­ney re­cently when Larry Sher­ertz sent me some fly­ing-squir­rel pho­tos he’d taken.

Fly­ing squir­rels are “in­cred­i­bly fast and fre­netic” and “ridicu­lously cute,” as Larry aptly de­scribed them. Be­ing noc­tur­nal, they have huge eyes to help them nav­i­gate in the dark, and they do what no other mam­mal in North Amer­ica can do — glide through the air, thanks to mem­branes con­nect­ing to their front and hind feet on each side. They are so ag­ile in flight that they can ac­tu­ally do a 180-de­gree turn in midair.

Al­though of­ten out­num­ber­ing gray squir­rels in some ar­eas, the fly­ing squir­rels’ se­cre­tive, noc­tur­nal life­style and pref­er­ence for liv­ing high in forests means that they are rarely seen by hu­mans. They will some­times take up res­i­dence in our at­tics, in which case we may hear them. And they will some­times visit houses at night if some­one leaves a few seeds and nuts out for them, as Larry does.

There are two species of fly­ing squir­rel in North Amer­ica — the south­ern ( Glau­comys volans) and the north­ern ( Glau­comys sabri­nus). The south­ern species, which is quite com­mon through­out the east­ern U.S. at el­e­va­tions be­low 3,200 feet, is a lit­tle more than 5 inches long, with a 4-inch tail. It eats a wide va­ri­ety of seeds, nuts and buds and, ac­cord­ing to the Vir­ginia Fish and Wildlife In­for­ma­tion Ser­vice (VaFWIS.org), is also the most car­niv­o­rous squir­rel in North Amer­ica, din­ing on in­sects, baby birds, eggs and even car­rion.

A bit big­ger and browner than its south­ern cousin, the north­ern fly­ing squir­rel is quite com­mon north of here, but in the Ap­palachi­ans of Vir­ginia, West Vir­ginia and North Carolina — the south­ern­most part of its range — it’s mostly found above 3,500 feet. It has evolved to have a more spe­cial­ized diet than the south­ern fly­ing squir­rel, pre­fer­ring food found in red­spruce ( Picea rubens) forests, which threat­ens the north­ern squir­rel’s sur­vival this far south.

These forests, which here oc­cur only at high el­e­va­tions on cool, damp, north-fac­ing slopes, are rapidly dis­ap­pear­ing — only 2 per­cent re­main, says naturalist Ron Hughes, a lands and fa­cil­i­ties man­ager for the Vir­ginia Depart­ment of Game and In­land Fish­eries. In the 1990s, as a grad­u­ate stu­dent, Ron par­tic­i­pated in a study of the Carolina fly­ing squir­rel ( Glau­comys sabri­nus col­oratus), which, along with the Vir­ginia ver­sion ( Glau­comys sabri­nus

fus­cus), are the sub­species of north­ern fly­ing squir­rel in­hab­it­ing the south­ern Ap­palachi­ans.

The loss of such high­el­e­va­tion bo­real forests “has been in­cred­i­bly fast,” Ron says, mak­ing them sec­ond only to the Ever­glades as “the most threat­ened habi­tat on this con­ti­nent.” Their de­struc­tion is mostly from hu­man ac­tiv­ity, in­clud­ing min­ing through moun­tain­top re­moval, log­ging, ridge-top de­vel­op­ment, in­tro­duced in­sect pests, acid rain and cli­mate change.

Through the in­creas­ing isolation of pop­u­la­tions on high-el­e­va­tion habi­tat “is­lands” at the south­ern end of the north­ern fly­ing squir­rel’s range, it has evolved into 28 sub­species. The south­ern fly­ing squir­rel, by con­trast, lives in ar­eas that over­lap more, and has evolved into only four sub­species. In Vir­ginia, for­est de­struc­tion has ma­rooned the north­ern species on habi­tat is­lands in four coun­ties, ac­cord­ing to VaFWIS: High­land, Mont­gomery, Grayson and Smyth.

While the north­ern fly­ing squir­rel may sup­ple­ment its diet with seeds, fruit, meat and buds, the “main­stay” of its diet are truf­fle-like fungi in the genus Elaphomyce­s, which are as­so­ci­ated with red-spruce forests, ac­cord­ing to an ar­ti­cle in the May/June is­sue of “Na­ture Con­ser­vancy Mag­a­zine” (mag­a­zine.na­ture. org).

The fate of the squir­rel is en­twined with that of the red spruce and the fungi through a com­plex sym­bi­otic re­la­tion­ship. Ba­si­cally, the fungi are my­c­or­rhizal, liv­ing un­der­ground and at­tached to the trees’ roots. They help the trees break down and take up nu­tri­ents and wa­ter and pro­tect the trees’ roots from harm­ful fungi and ne­ma­todes. Be­cause the fungi are un­der­ground, they rely on a specialist like the squir­rel in or­der to re­pro­duce and spread. The squir­rel eats the fungi, dis­pers­ing their spores when it defe­cates.

Some re­searchers, in­clud­ing Ron, say the sym­bi­otic na­ture of the squir­rel’s re­la­tion­ship to the fungi may mean it’s a key­stone species of the red spruce for­est ecosys­tem — if the squir­rel dis­ap­pears, the for­est could also. The fungi make up the ma­jor por­tion of the squir­rel’s diet — up to 98 per­cent in the Pa­cific North­west, ac­cord­ing to one study. Ron adds that the squir­rel’s diet can be more var­ied in the south­ern Ap­palachi­ans.

In the study of the Carolina fly­ing squir­rel in North Carolina, the study area was sim­i­lar to those of high-el­e­va­tion red spruce forests, but the for­est there was al­most de­void of conifers, Ron says. So what were the squir­rels eat­ing? Ron sug­gests it may be dif­fer­ent my­c­or­rhizal fungi that are as­so­ci­ated with er­i­ca­ceous shrubs, which were also in the study area, in­clud­ing lau­rel, blue­berry and rhodo­den­dron. He adds that more re­search on the squir­rel’s diet is needed.

The lack of suit­able fungi at lower el­e­va­tions in the south­ern Ap­palachi­ans — and the north­ern fly­ing squir­rel’s vul­ner­a­bil­ity to preda­tors, par­a­sites and dis­eases there — will likely keep the squir­rel at high el­e­va­tions, threat­en­ing its sur­vival there, Ron says. The Carolina fly­ing squir­rel and the Vir­ginia (aka West Vir­ginia) vari­ant, which are the only sub­species found in Vir­ginia, are listed as en­dan­gered on state and federal lists.

“Their plight in the Ap­palachi­ans started when hu­mans started to de­stroy all the spruce forests,” Ron ex­plains. These forests de­pend on a rich sub­strate of hu­mus to sur­vive. In re­turn, the trees pro­vide shade and slow runoff, which pro­tects the sub­strate. Once the trees are re­moved, Ron says, the peat- like sub­strate dries out and fires are more likely to oc­cur, de­stroy­ing it for­ever, along with the spruces’ seeds.

While the south­ern and north­ern fly­ing squir­rel species, “do not like each other,” ac­cord­ing to Ron, their ranges can over­lap a bit at higher el­e­va­tions. There, they will of­ten use the same nest­ing sites, in­clud­ing wood­pecker holes, or the for­mer nests of birds and other squir­rels. This has led to a fur­ther stres­sor on the north­ern species: An in­testi­nal ne­ma­tode car­ried by the south­ern species that has lit­tle ef­fect on that car­rier but kills north­ern fly­ing squir­rels, ac­cord­ing to a Jan­uary 2010 ar­ti­cle in the “Jour­nal of Wildlife Dis­eases.”

While only the south­ern fly­ing squir­rel is likely to be spotted in Rap­pa­han­nock these days, “un­til pretty re­cently there were prob­a­bly north­ern fly­ing squir­rels in Shenan­doah Na­tional Park,” Ron says. Al­though sur­veys for them done around Hawks­bill Moun­tain did not turn up any ev­i­dence, “I bet you that a pretty good per­cent­age of the park above 3,200 feet el­e­va­tion had spruce on it,” he adds, bas­ing this on the rem­nant bal­sam fir trees that are still there.

While sev­eral con­ser­va­tion or­ga­ni­za­tions and govern­ment agencies have united in West Vir­ginia to refor­est ar­eas where red spruce has been de­stroyed so north­ern fly­ing squir­rel pop­u­la­tions can re­bound,, Ron says no such ef­fort is un­der­way in Vir­ginia.

BY LARRY SHER­ERTZ

Al­though leav­ing out bird feed­ers can at­tract some very un­wel­come vis­i­tors, a bit of seed left out here in Rap­pa­han­nock can at­tract a com­mon yet rarely seen noc­tur­nal denizen of Vir­ginia’s forests, the south­ern fly­ing squir­rel.

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