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Macrotus californicus

Baird, 1858

California Leaf-nosed Bat

G3Vulnerable (G3G4) Found in 1 roadless area NatureServe Explorer →
G3VulnerableGlobal Rank
Least concernIUCN
High - mediumThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.100867
Element CodeAMACB01010
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVertebrate Animal
IUCNLeast concern
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomAnimalia
PhylumCraniata
ClassMammalia
OrderChiroptera
FamilyPhyllostomidae
GenusMacrotus
Other Common Names
California leaf-nosed bat (EN) Un Murciélago (ES)
Concept Reference
Wilson, D. E., and D. M. Reeder (editors). 1993. Mammal species of the world: a taxonomic and geographic reference. Second edition. Smithsonian Institution Press, Washington, DC. xviii + 1206 pp. Available online at: http://www.nmnh.si.edu/msw/.
Taxonomic Comments
This species was regarded as a subspecies of M. waterhousii by Anderson and Nelson (1965) and Hall (1981).
Conservation Status
Rank MethodLegacy Rank calculation - Excel v3.1x
Review Date2014-10-31
Change Date2014-05-22
Edition Date2015-03-30
Edition AuthorsHammerson, G.
Threat ImpactHigh - medium
Range Extent200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Rank Reasons
Fairly large range in southwestern North America; many roost sites and locations; large population size; trend uncertain but probably not rapidly declining; threatened mainly by human entry into mine or cave roosts (disturbance may lead to abandonment) and closure or improper gating of mines for hazard abatement or renewed mining.
Range Extent Comments
Range extends from Baja California, Sonora, northern Sinaloa, and southwestern Chihuahua, Mexico, north to southern California, southern and western Arizona, and southern Nevada (Jones and Carter 1976). Elevational range extends to around 1,300 meters; to around 600 meters in California, 1,220 meters in Arizona.

Anderson and Nelson (1965) and Anderson (1969) included populations in Tamaulipas in the range of californicus, based on morphological similarities to specimens from Arizona. Hall (1981), Koopman (in Wilson and Reeder 1993) and Simmons (in Wilson and Reeder 2005) also included Tamaulipas in the range of this species, evidently all following Anderson and Nelson (1965). Greenbaum and Baker (1976) included these areas and all of eastern and southern Mexico in the range of M. waterhousii, which occurs in contiguous areas of eastern Mexico.
Occurrences Comments
The number of distinct occurrences has not been determined using standardized/meaningful criteria, but this species is represented by a widely distributed and large number of collection and observation sites (e.g., roosts) and locations (as defined by IUCN). This species is known from several dozen (>100) sites in Arizona (Arizona Game and Fish Department map, 2014).
Threat Impact Comments
Primary threats are human entry into mine or cave roosts (disturbance may lead to abandonment) and closure or improper gating of mines for hazard abatement or renewed mining. Loss of desert riparian habitat (as in the development of golf courses and housing areas in the Coachella Valley, California) likely also has contributed to population declines (P. E. Brown, Western Bat Working Group species account, 2005; Arizona Game and Fish Department).

Various forms of pollution might negatively affect this species, but the population impact is unknown. Climate change may affect the food resources and habitat of this species, but the likely severity of this threat over the next 10 years or three generations is uncertain.
Ecology & Habitat

Description

A large-eared, grayish or brown bat with a leaflike flap of thick skin projecting upward from the tip of the nose; ears (about 29-38 mm long) are joined at the base by a ridge of skin; tail extends 5-10 mm beyond tail membrane; total length usually less than 103 mm; upper incisors fill all of the space in front of the canines; forearm averages about 50 mm; interorbital region is 3.8 mm or less (Hoffmeister 1986, Ingles 1965).

Diagnostic Characteristics

Differs from Leptonycteris and Choeronycteris in Arizona in having a shorter rostrum, no bristlelike papillae on the tongue, first upper incisor in contact with the canine and usually also in contact with the second premolar, ears joined together near the base, and a larger number of chromosomes (2N=40 vs. 2N=32 or 16) (Hoffmeister 1986). Differs from M. waterhousii by having chromosomes 2N=40 rather than 2N=46, interorbital width of 3.8 mm or less, smaller canines, larger ears, and larger auditory bullae (Davis and Baker 1974, Anderson and Nelson 1965; see also Hoffmeister 1986).

Habitat

These bats inhabit lowland desert scrub. Day roosts are in caves or abandoned mine tunnels (today most often the latter) (Brown and Berry 1998, Brown 2006). Small groups may also use natural rock shelters in canyon walls. Most diurnal winter roosts are in warm mine tunnels at least 100 meters long (Bell et al. 1986; P. E. Brown, Western Bat Working Group species account, 2005). Night roosts are in open buildings, porches, rock shelters, mines, under bridges, or in various other sites. Maternity roosts are in warm sites in old mine tunnels or caves, in mines or areas separate from those used in winter (P. E. Brown, Western Bat Working Group species account, 2005).

Ecology

These bats roost singly or in groups of up to several hundred individuals, but individuals do not cluster. Males live in small bachelor groups in July and August, join females in September.

Reproduction

Insemination, ovulation, and fertilization occur mainly in late September-early October; embryonic development is delayed, gestation lasts about 8 months (Anderson 1969). Adult females bear usually 1 young between mid- May and mid-July. Young are weaned in about 1 month. Females first breed in their first fall, males the following year. Maximum life expectancy is estimated at more than 10 years (Anderson 1969). Females form maternity colonies of about 100-200 adults, including a few males, though males may form large roosts of their own at this time..
Terrestrial Habitats
DesertCliff
Palustrine Habitats
Riparian
Other Nations (1)
United StatesN3
ProvinceRankNative
ArizonaS3Yes
NevadaS2Yes
CaliforniaS3Yes
Threat Assessments
ThreatScopeSeverityTiming
1 - Residential & commercial developmentSmall (1-10%)Moderate - slightHigh (continuing)
2 - Agriculture & aquaculture—Negligible or <1% pop. declineHigh (continuing)
3 - Energy production & miningSmall (1-10%)Extreme - seriousHigh (continuing)
3.2 - Mining & quarrying——High (continuing)
4 - Transportation & service corridorsSmall (1-10%)Negligible or <1% pop. declineHigh (continuing)
5 - Biological resource useNegligible (<1%)—High (continuing)
6 - Human intrusions & disturbanceLarge - restrictedModerate or 11-30% pop. declineHigh (continuing)
6.1 - Recreational activities——High (continuing)
7 - Natural system modificationsNegligible (<1%)Negligible or <1% pop. declineHigh (continuing)
8 - Invasive & other problematic species, genes & diseases—Negligible or <1% pop. declineHigh (continuing)
9 - PollutionUnknownUnknownHigh (continuing)
10 - Geological eventsNegligible (<1%)——
11 - Climate change & severe weatherPervasive (71-100%)UnknownHigh (continuing)

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Roadless Areas (1)
Arizona (1)
AreaForestAcres
Black CrossTonto National Forest5,966
References (65)
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