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A Synopsis of the American Bats of the Genus Pipistrellus

E. RAYMOND HALL and WALTER W. DALQUEST

University of Kansas Publications Museum of Natural History

Volume 1, No. 26, pp. 591-602, 1 figure in text January 20, 1950

University of Kansas LAWRENCE 1950

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Edward H. Taylor, A. Byron Leonard, Robert W. Wilson

Volume 1, No. 26, pp. 591-602, 1 figure in text January 20, 1950

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1950

23-1546

A Synopsis of the American Bats of the Genus Pipistrellus

E. RAYMOND HALL AND WALTER W. DALQUEST

Four nominal species of the genus Pipistrellus are currently recognized in North America. They are Pipistrellus subflavus (F. Cuvier) of eastern North America, Pipistrellus hesperus (H. Allen) of western North America, Pipistrellus veracrucis (Ward) from Veracruz, Mexico, and Pipistrellus cinnamomeus Miller from Tabasco, Mexico.

In the past three years, specimens have been obtained in Veracruz (by Dalquest) of each of the southern species. One of these, P. cinnamomeus, previously was known from a single specimen; the other, P. veracrucis, was known only from six specimens which now are lost or misplaced. The results of our study of these recently acquired Mexican specimens constitute our principal contribution in this paper; we have done little more with the material from the United States and Canada than to codify the findings of other mammalogists with respect to the systematic status and geographic distribution.

Study of the available specimens reveals that there are only two species, Pipistrellus hesperus and Pipistrellus subflavus; Pipistrellus veracrucis proves to be only a subspecies (geographic race) of P. subflavus, and Pipistrellus cinnamomeus proves to be a species of another genus, Myotis (see Hall and Dalquest, page 583 of this volume).

Genus +Pipistrellus+ Kaup

1829. Pipistrellus Kaup, Skizzirte Entw.-Gesch. u. natuerl. Syst. europ. Thierw., Vol. 1, p. 98, Type, Vespertilio pipistrellus Schreber (not seen by us, after Miller, N. Amer. Fauna, 13:87, 1897).

Range in the New World.--In North America from southern Canada to Honduras (47 degrees to 5 degrees North Latitude) and from the Atlantic to the Pacific; not recorded from the West Indies or South America.

Characters.--Size small; tail approximately as long as outstretched leg; ears well developed with prominent tragus; dental formula: i.2/3; c.1/1; p.2/2; m.3/3; two upper incisors subequal and outer one lacking a concavity on surface facing canine; dentition otherwise essentially as in Myotis Kaup except that third premolar is always, instead of rarely, absent.

Remarks.--There are two species in North America. Their geographic ranges, as now known, meet, but do not overlap. Certain differences between the two species are listed in the parallel columns below. Most of these differences in the skull and teeth are illustrated in figures 22 and 23 on page 92 of Miller's "Revision of the North American bats of the family Vespertilionidae (N. Amer. Fauna, 13, 1897)."

====================================================================== Structure | P. hesperus | P. subflavus ====================================================================== Color | Predominately gray | Predominately brown --------------------+-------------------------+----------------------- Foot | Less than half as long | More than half as long | as tibia | as tibia --------------------+-------------------------+----------------------- Thumb, length of | Less than 4.9 mm. | More than 4.9 mm. --------------------+-------------------------+----------------------- Tragus | Blunt, terminal part | Narrow, straight | bent forward | --------------------+-------------------------+----------------------- Skull | Nearly straight | Dish-faced (dorsal profile) | | --------------------+-------------------------+----------------------- Braincase | Small | Large (viewed from above) | | --------------------+-------------------------+----------------------- Palate | Extending far behind | Extending short | molars; spine short, | distance behind | | molars; spine long, | narrow at base | wide at base --------------------+-------------------------+----------------------- I2 | Unicuspidate | Bicuspidate --------------------+-------------------------+----------------------- I3 | Accessory cusp present | Accessory cusp absent | on anterointernal | on anterointernal | face | face --------------------+-------------------------+----------------------- P1 (occlusal view) | Less than a seventh as | More than a seventh | large as canine | as large as canine --------------------+-------------------------+----------------------- P1 (labial view) | Concealed by C1 and P4 | Not concealed --------------------+-------------------------+----------------------- P4 | Touching canine | Not touching canine --------------------+-------------------------+----------------------- i3 | Touching i2 and c1 | Separated by space | | from i2 and c1 --------------------+-------------------------+----------------------- p3 | Lower than anterior | As high as anterior | cusp of canine | cusp of canine --------------------+-------------------------+----------------------- Distance from c1 | Less than length of m2; | More than length of to m1 | premolars crowded | m2; premolars less | | crowded --------------------+-------------------------+-----------------------

+Pipistrellus hesperus+

(Synonomy under subspecies)

Range.--Arid Sonoran life-zones of western North America from Washington southward to Jalisco.

Characters.--Smoke Gray to Buff Brown (Capitalized color terms after Ridgway, Color Standards and Color Nomenclature, Washington, D. C., 1912) dorsally; total length, 60 to 86; foot less than half as long as tibia; tragus blunt with terminal part bent forward; skull nearly straight in dorsal profile; inner upper incisor unicuspidate; outer upper incisor with accessory cusp on anterointernal face; P1, viewed from occlusal face, less than a seventh of area of canine, and from labial aspect concealed by canine and fourth premolar; lower, third premolar lower than anterior cusp of canine; lower premolars crowded, distance between canine and first molar less than length of second lower molar.

Remarks.--In the United States and in the northern part of Mexico, P. hesperus is the smallest bat found. Little is known about its habits. It emerges earlier in the evening than other species of bats. The frequency with which it is seen near cliffs suggests that it finds concealment under rocks. In winter, in Nevada (Hall, Mammals of Nevada, p. 150, 1946), P. hesperus has been found singly in crevices in the roofs of mine tunnels.