Natural History of the Prairie Vole (Mammalian Genus Microtus) Part 2

TABLE 6.--_Frequency of Occurrence of Fleas on Seven Species of Small Mammals_[E]

Column headings:

A: _Cryptotis parva_ B: _Blarina brevicauda_ C: _Peromyscus maniculatus_ D: _Peromyscus leucopus_ E: _Sigmodon hispidus_ F: _Microtus ochrogaster_ G: _Pitymys nemoralis_

A B C D E F G ---------------------------------------------------------------- _Orchopeas leucopus_ (Baker) 0 0 53 31 37 6 10 _Orchopeas howardii_ (Baker) = _O. wickhami_ (Baker) 0 0 0 0 0 1 0 _Nosopsyllus fasciatus_ (Bosc) 0 0 0 0 0 1 0 _Epitedia wenmanni_ (Rothschild) 0 0 0 9 0 2 0 _Rectofrontia fraterna_ (Baker) 0 0 0 0 0 1 0 _Corrodopsylla hamiltoni_ (Traub) 47 8 0 0 0 0 0 _Ctenophthalmus pseudagyrtes_ Baker 0 38 0 0 4 25 53 _Peromyscopsylla scotti_ I. Fox 0 0 0 6 0 0 0 -------------------------- Total number examined 34 13 34 35 57 414 21 ----------------------------------------------------------------

[Footnote E: The numbers represent the percentage of each species which was parasitized by fleas. The mammals were collected at Lawrence, Douglas County, Kansas, between October, 1945, and June, 1946. These data are entirely from snap-trapped animals with the exception of those from _Microtus_ and _Pitymys_ which are from both snap-trapped and live-trapped animals.]

It is seen that some fleas are rather specific in their choice of hosts, and that others are commonly found on two or more small mammals in the same habitat. In each of these groups there are fleas which have a habitat preference, that is to say, the flea lives on the host when the host lives in a given habitat, but is absent when the host lives in another habitat.

GROUP 1: FLEAS WITH A HOST PREFERENCE

_Epitedia wenmanni_ was found on the white-footed mouse (_Peromyscus leucopus_) and only rarely on the prairie vole. _Corrodopsylla hamiltoni_ was taken only from the two kinds of shrews (_Blarina brevicauda_ and _Cryptotis parva_). Fleas on shrews may have a well-developed host preference. At any rate, Elton, Baker, Ford, and Gardner (1931) found that _Doratopsylla dasycnemus_ rarely strayed from its normal host (_Sorex araneus_) to other small mammals.

_Peromyscopsylla scotti_ was taken from the white-footed mouse (_Peromyscus leucopus_), and had a habitat preference also. It was found only on those white-footed mice which were trapped in the woodlands at various places in Douglas County; white-footed mice which were trapped in areas of brush were free of this parasite.

GROUP 2: FLEAS COMMONLY FOUND ON TWO OR MORE KINDS OF SMALL MAMMALS

_Orchopeas leucopus_ was an outstanding example of this group. It was the most common flea on the deer mouse, the white-footed mouse, and the cotton rat. In certain areas it was common on the two voles (_Pitymys nemoralis_ and _Microtus ochrogaster_). _Ctenophthalmus pseudagyrtes_ is the most abundant flea on the two kinds of voles and on the large shrew (_Blarina brevicauda_), and was found sparingly on the cotton rat.

Several kinds of fleas do not belong in either of the above groups. Some fleas were accidental strays from mammals not included in table 6; and one flea (_Rectofrontia fraterna_) may prove to be a common nest parasite. _Orchopeas howardii_ is common on tree squirrels (_Sciurus niger_ and _S. carolinensis_). _Nosopsyllus fasciatus_ is a cosmopolitan flea on _Rattus norvegicus_. _Rectofrontia fraterna_ was taken once from a prairie vole. Since the only specimens in the University of Kansas Entomological Collections are from "mouse nests," this flea may be found to be a nest inhabiting parasite.

Some fleas are possible bridges by which a blood parasite could be transmitted from one kind of a mammal to another. If _Ctenophthalmus pseudagyrtes_ acted as the intermediate host of a disease-causing organism, an epizootic from _Microtus ochrogaster_ might be transmitted to _Pitymys nemoralis_ or to _Sigmodon hispidus_ or _Blarina brevicauda_. There are several other such potential bridges for blood parasites. Although table 6 does not prove that individual fleas wander from one host to another, the frequency with which the several kinds of fleas are removed from live mice suggests that the fleas occasionally do so.

LICE (ANOPLURA)

Lice collected from the prairie vole were all of one species, _Hoplopleura acanthopus_ (Burmeister). Of 59 voles examined for the presence of lice, 33 were found to be parasitized; the 59 voles had an average of 3.4 lice each. Other mice which used the same runways as the prairie vole had their own species of Anoplura. The cotton rat was host to _Hoplopleura hirsuta_ Ferris, and the two species of _Peromyscus_ were parasitized by _Hoplopleura hesperomydis_ (Osborn).

The writer collected _Hoplopleura acanthopus_ from _Microtus californicus_ at Calaveras Dam, Alameda County, California, and from _M.

pennsylvanicus_ at Ithaca, Tompkins County, New York. Elton, Ford, Baker, and Gardner (1931) recorded this same species from _M. argestis_ in England.

Lice on the prairie vole are the same species as those found on other species of _Microtus_ in other areas, but since Anoplura of the prairie vole do not parasitize the cotton rat, the white-footed mouse, and the deer mouse, this host specificity of lice makes it unlikely that lice would carry blood parasites from the prairie vole to any of the latter named rodents.

MITES (ACARINA EXCEPT IXODOIDEA)

Many of the small mammals examined in this study had mites, some of which were collected and identified. Mites were collected from other species of voles in several localities in the United States and in one locality in Canada; as voles in widely separated regions are sometimes hosts to the same species of mites, these records will be presented here.

The frequency of some kinds of mites in the identified material suggests that they are more abundant than other kinds. The occurrence of mites on small mammals from Lawrence, Kansas, is presented in table 7.

The following comments can be made concerning the specificity and geographic ranges of several species of mites:

_Liponyssus occidentalis_ Ewing was found only on _Cryptotis parva_.

_Eulaelaps stabularis_ (Koch) was one of the more common kinds found on the prairie vole. This mite is rather large (about 1 mm. long) and is frequently (with the following species) seen running through the pelage of its host. In addition to the records for this species in table 1, it was found to be a common parasite on _Pitymys pinetorum_ at Point Abino, Welland County, Ontario. Elton, Ford, Baker and Gardner (1931) found this same mite on _Apodemus sylvaticus_ and _Clethrionomys glareolus_ in England.

_Atricholaelaps glasgowi_, like the preceding species, was one of the commoner mites on the prairie vole. It was found also on _Pitymys pinetorum_ at Point Abino, Welland County, Ontario; on _Microtus pennsylvanicus_ at Ithaca, Tompkins County, New York; and on _M.

californicus_ at Calaveras Dam, Alameda County, California.

_Atricholaelaps sigmodoni_ occurred only on the cotton rat.

_Laelaps kochi_ was less commonly found than _Eulaelaps stabularis_ and _Atricholaelaps glasgowi_. In Kansas the prairie vole and the cotton rat were hosts to _Laelaps kochi_, and it occurred on _Microtus pennsylvanicus_ at Ithaca, New York, and on _M. californicus_ at Berkeley, California.

Trombiculidae are commonly known by their larvae which are called chiggers or harvest mites. The white-footed mouse, the cotton rat, and the prairie vole were parasitized at Lawrence. In the winter these mites live in the ears of these small mammals, but in the summer they were found both in the ears and on the rump. Those obtained in winter were _Ascoschongastia brevipes_ (Ewing); other species may be involved.

Listrophoridae was represented on the prairie vole by a species of _Myocoptes_ and a species of _Listrophorus_. These mites cling to the hairs of their host, and do not occur on the skin of the voles.

No evidence was seen that mites had any ill effect on the health of their hosts. No voles had scabs on the skin; and the ears were not swollen and disfigured as they sometimes are by chiggers. Although the ident.i.ty of a specimen of mite could not be determined until it was mounted, a person could tell whether or not it was one of the larger, very active Laelaptidae, one of the hair-clinging Listrophoridae, or one of the tiny, orange Trombiculidae.

On July 12, 1946, three prairie voles were examined to determine the number of mites they supported. The voles were freshly caught, no one of them having been dead for more than five minutes before they were examined. These three voles had an average of 25 Laelaptidae, 22 Listrophoridae, and 53 Trombiculidae.

Six species of mites (Ixodoidea excepted) were found on the prairie vole. Four of these were collected also from other small mammals living in the same habitat as this vole. Two species of mites were found to occur on voles in New York, Kansas, and California.

TICKS (IXODOIDEA)

Two kinds of ticks were found. One adult specimen of _Ixodes sculptus_ Neumann was clinging to the head of a vole, just in front of its eye.

This species of tick was taken also from the thirteen-lined ground squirrel (_Citellus tridecimlineatus_) at Lawrence. One nymph of _Dermacentor variabilis_ (Say) was found attached to the scapular region of a prairie vole. Both of these specimens were taken in June.

TABLE 7. _Host Distribution of Mites on Seven Small Mammals_[F]

Column headings:

A: _Scalopus aquaticus_ B: _Cryptotis parva_ C: _Blarina brevicauda_ D: _Peromyscus maniculatus_ E: _Peromyscus leucopus_ F: _Sigmodon hispidus_ G: _Microtus ochrogaster_

A B C D E F G ------------------------------------------------------------------------- _Ascoschongastia brevipes_ (Ewing) .. .. .. .. X X X _Liponyssus occidentalis_ Ewing .. X .. .. .. .. ..

_Eulaelaps stabularis_ (Koch) X X X .. X .. X _Atricholaelaps glasgowi_ (Ewing) .. .. .. X .. .. X _Atricholaelaps sigmodoni_ Strandtmann .. .. .. .. .. X ..

_Laelaps kochi_ Oudemans .. .. .. .. .. X X _Myocoptes_ sp. .. .. .. .. .. .. X _Listrophorus_ sp. .. .. .. .. .. .. X -------------------------------------------------------------------------

[Footnote F: These data are from material collected at Lawrence, Douglas County, Kansas.]

REPRODUCTION

AGE CLa.s.sES

Each prairie vole was a.s.signed to one of three age cla.s.ses (juvenile, subadult, or adult) princ.i.p.ally on the basis of weight, but partly on the quality and color of the pelage. The three age cla.s.ses are characterized in table 8.

TABLE 8. _Characters of Juvenile, Subadult, and Adult Prairie Voles_

Juvenile Subadult Adult