Eumops floridanus ( Allen, 1932 )

Vannatta, Jessica M, Gore, Jeffery A, Mathis, Verity L & Carver, Brian D, 2021, Eumops floridanus (Chiroptera: Molossidae), Mammalian Species 53 (1009), pp. 125-133 : 125-129

Eumops floridanus ( Allen, 1932)

Florida Bonneted Bat

Molossides floridanus G. M. Allen, 1932:257 . Type locality “Melbourne, Brevard County, Florida,” United States.

Eumops floridanus: Ray et al., 1963:377 . First use of current name combination.

Eumops glaucinus floridanus: Koopman, 1971:5 . Name combination.

CONTEXT AND CONTENT. Order Chiroptera , suborder

Yangochiroptera, superfamily Molossoidea , family Molossidae ,

subfamily Molossinae , genus Eumops . Eumops floridanus is monotypic ( Timm and Genoways 2004). Eger (1977) and

Koopman (1971) reviewed Eumops specimens from Florida and considered them a well-marked subspecies of E. glaucinus

( E. glaucinus floridanus ). Subsequently, Timm and Genoways

(2004) conducted a more extensive evaluation of morphological features of Eumops specimens from Florida and, based primarily on cranial and bacular differences, proposed that the Florida form is a separate species, E. floridanus . Cytochrome- b data, however, suggest that E. floridanus is genetically similar to E. ferox Fig. 1. —An adult Eumops floridanus from Charlotte County, Florida. ( McDonough et al. 2008; Bartlett et al. 2013). Apparently, the PhotographbyJ.Gore (FloridaFishandWildlifeConservationCommission). geographic isolation of E. floridanus on the Florida peninsula has allowed morphological distinction to precede significant genetic differentiation ( McDonough et al. 2008).

DIAGNOSIS

Eumops floridanus is the largest species of bat in Florida and the only member of the genus Eumops in Florida (Fig. 1). However, it is similar in appearance to other members of the Eumops glaucinus complex, including Wagner’s bonneted bat ( E. glaucinus ) found in Colombia, Venezuela, and Paraguay; the fierce bonneted bat ( E. ferox ) found in Cuba, Jamaica, and parts of Mexico and Central America; and Wilson’s bonneted bat ( E. wilsoni ) found in Ecuador and Peru ( McDonough et al. 2008; Baker et al. 2009; Bartlett et al. 2013; but see Gregorin et al. 2016). Eumops floridanus can be differentiated from its close relatives by its larger body mass (27.0–59.0 g), longer forearm (57.9–69.2 mm), longer skull (25.2–27.2 mm) with a narrower palate, and deeper basisphenoid pits (1.30–1.55 mm) that are short relative to condylobasal length (5.35–6.18%— Owre 1978; Timm and Genoways 2004; Ober et al. 2017b). In addition, other cranial measurements (mm), such as condylobasal length (23.4–25.4), zygomatic breadth (15.1– 17.3), interorbital constriction (7.9–9.2), mastoid breadth (13.5–14.7), palatal length (10.1–11.2), and length of maxillary toothrow (9.4–10.6) are on average larger in E. floridanus compared to others in the E. glaucinus complex (see Eger 1977 and Timm and Genoways 2004 for detailed descriptions and measurements). The baculum of E. floridanus differs from that of other similar Eumops species by being longer (0.70 mm) and having a base nearly equal in width to the shaft (0.10 mm — Timm and Genoways 2004). Gregorin et al. (2016) proposed that Underwood’s bonneted bat ( E. underwoodi ) from Central America, Mexico, and the southwestern United States and the big bonneted bat ( E. dabbenei ) from South America be included in the E. glaucinus complex. However, E. floridanus is smaller in size (forearm length: 57.9–69.2 mm), especially compared to E. dabbenei (forearm length: 77.1–85.7; E. underwoodi forearm length: 65.3–76.3), and the distribution of E. floridanus does not overlap with that of either species ( Kiser 1995; McWilliams et al. 2002). Eumops floridanus can be differentiated from the only other molossid bat in Florida, the Brazilian free-tailed bat ( Tadarida brasiliensis ), by its large size, smooth upper lip, and ears that connect at the base ( Fig. 2 ; Marks and Marks 2006; Florida Fish and Wildlife Conservation Commission [FWC] 2013).

GENERAL CHARACTERS

Eumops floridanus is a large molossid bat found only in the southern one-half of peninsular Florida ( Timm and Genoways 2004; Bailey et al. 2017b). Primary external characteristics are large, forward-pointing ears that join at the base, a smooth upper lip ( Fig. 2 ), and a tail that extends beyond the uropatagium ( Eger 1977; Owre 1978; Marks and Marks 2006). The fur is bicolored with a light base and generally a dark gray to brown tip on the dorsum and a light gray tip on the venter ( Marks and Marks 2006). Many individuals have patches of hypopigmented fur, usually on the center of the abdomen ( Fig. 3 ), and these white markings vary from small spots to bands across the abdomen ( Smith et al. 2019). The proportion of individuals with this abnormal and genetically linked color varies across the distribution, but 80.8% of individuals (n = 213) captured from a population in Charlotte County, Florida had white markings, which is the highest known incidence of hypopigmentation for a population of bats ( Smith et al. 2019).

Eumops floridanus is sexually dimorphic, with males generally having slightly longer forearms and longer and wider wings than females ( Ober et al. 2017b). Males also have functional gular glands ( Fig. 3 ), which are distinct sebaceous glands on the throat that change in appearance with reproductive status and are most obvious on large, reproductively active males ( Ober et al. 2017b).

Ober et al. (2017b) recorded forearm lengths (60.0– 69.1 mm) and body masses (27–59 g) for 201 E. floridanus of mixed sexes, ages, and reproductive statuses from Charlotte County. The mean mass (± SD) of 16 nonreproductive, adult males was 40.68 ± 5.79 g and for 46 nonreproductive, adult females, it was 40.47 ± 3.32 g ( Ober et al. 2017b). The mean mass (± SD) for 31 reproductively active, adult males was 43.77 ± 4.38 g, whereas it was 45.29 ± 2.96 g for 59 postlactating adult females and 47.13 ± 4.10 g for 56 pregnant females ( Ober et al. 2017b). A sample of nine E. floridanus had the following measurements (mm): total body length (130–165), wingspan (490–530), tail length (46– 57), length of hind foot (11–15), ear length (20–30), and forearm length (60.8–66.0— Timm and Genoways 2004). A sample of 10 individuals had the following measurements (mm or g): total length (134–165), forearm length (57.9–69.2), length of hind foot (10.8–12.0), length of ear from notch (19.9–28.0), and body mass (30.2–43.5— Owre 1978). The tragus lengths of four adult individuals in the University of Florida (UF), Florida Museum of Natural History (FLMNH) were 3.0 and 3.5 mm for two males and 4.0 and 4.5 mm for two females (UF 10923, 11436, 11437, and 31477).

Eumops floridanus has a broad skull with large orbits ( Fig. 4 ). Ranges of skull measurements (mm) for 28 individuals from several Florida counties were: skull length (25.2–27.2), condylobasal length (23.4–25.4), zygomatic breadth (15.1– 17.3), interorbital constriction (7.9–9.2), postorbital constriction (5.1–5.7), mastoid breadth (13.5–14.7), palatal length (10.1–11.2), length of maxillary toothrow (9.4–10.6), and breadth across upper molars (9.4–11.4— Timm and Genoways 2004). The dental formula is i 1/2, c 1/1, p 2/2, m 3/3, total 30 ( Eger 1977). Based on measurements from seven individuals in Florida, the length (mm) of m1 was 2.7 (2.6–2.8), m2 was 2.7 (2.6–2.7), M1 was 2.6 (2.5–2.6), M2 was 2.5 (2.4–2.6), and M3 was 3.4 (3.2–3.6— Morgan 1985, 1991).

DISTRIBUTION

Eumops floridanus is restricted to the southern one-half of the Florida peninsula, and its distribution is likely among the smallest of any bat species in North America ( Fig. 5 ; Belwood 1992; Timm and Genoways 2004). Interestingly, the first specimen was not recorded until 1936 ( Barbour 1936), and no specimens were found outside the Miami area until 1979 when a small colony was discovered on the west coast of Florida ( Belwood 1981). Interest in E. floridanus increased after it was recognized as a full species and listed as “Endangered” (EN) in 2013 ( United States Fish and Wildlife Service [USFWS]). With additional research, the distribution is now known to include Broward, Charlotte, Collier, Desoto, Glades, Hendry, Highlands, Lee, Miami-Dade, Monroe, Okeechobee, Palm Beach, and Polk counties ( Fig. 5 ; Belwood 1992; USFWS 2013; Angell and Thompson 2015; Braun de Torrez et al. 2016, 2017, 2018b; Bailey et al. 2017b). The northern boundary of its distribution is likely limited by minimum temperatures in winter and spring months ( Bailey et al. 2017 a, 2017b). During an extended period of cold weather in mandible from a Pleistocene deposit at the type locality in Florida, and Morgan (1991) provided cranial and mandibular measurements from fossils from Vero Beach. Comparisons of fossil specimens to a recent sample of seven individuals from near Miami revealed that dental measurements were nearly identical between fossil and recent specimens, although measurements of the ramus were larger for fossil specimens ( Morgan 1991). All fossil specimens discovered thus far are from the east coast of Florida, and interestingly, two of the four fossil sites are north of the current known distribution of E. floridanus ( Fig. 5 ; Allen 1932; Ray et al. 1963; Morgan 1985). As Koopman (1971) noted, it is not known why those fossil localities are devoid of living populations.

January and February of 2010, at least eight E. floridanus in a bat house in North Fort Myers, Florida died, presumably due to hypothermia (USFWS 2013). Although E. floridanus appears to be restricted to the subtropical climate of south Florida, its distribution may extend farther north than is currently known, and further surveying is warranted to confirm the northern extent of the distribution ( Bailey et al. 2017b).

FOSSIL RECORD

Fossil specimens of Eumops floridanus were discovered before any recent individuals were known ( Allen 1932; Timm and Genoways 2004). In 1929, a lower jawbone from E. floridanus was found in a Pleistocene (late Rancholabrean) deposit in Melbourne, Brevard County, Florida, which was designated the type locality ( Allen 1932; Ray et al. 1963). Subsequent fossil specimens included a Pleistocene fossil mandible from Monkey Jungle Hammock in Miami-Dade County ( Martin 1977), nine Holocene fossils from Vero Beach, Indian River County ( Morgan 1985), and a Holocene fossil of a proximal radius from near Monkey Jungle Hammock ( Morgan 1991). Allen (1932) provided measurements of a fossil

FORM AND FUNCTION

Eumops floridanus has a mid-sized wing aspect ratio and shorter and broader wings than other Eumops species, which may prevent it from flying for long distances or as fast as other closely related molossids ( Ober et al. 2017b). The average wing aspect ratio of E. floridanus (n = 67; ¯x ± SD) from Charlotte County was 2.88 ± 0.06 mm, while the wing shape index for the same individuals was 1.84 ± 0.04 mm, and the wing tip index was 63.96 ± 0.46 mm ( Ober et al. 2017b). The wing aspect ratio of E. floridanus likely results in lower metabolic costs while flying in cluttered habitats at slow speeds but higher metabolic costs while flying in more open areas as compared to other Eumops species ( Ober et al. 2017b). Male E. floridanus had wider wings (n = 29, ¯x = 62.02 ± 1.54 mm) than females (n = 38, 60.46 ± 1.67 mm) and longer wings (113.73 ± 2.89 mm) than females (111.65 ± 2.92 mm — Ober et al. 2017b). However, wingtip width (combined length of the first and second phalanges of the fourth finger) did not differ between the sexes, and lengths of the first and second phalanges were similar between males and females ( Ober et al. 2017b). Body condition index (BCI = mass/forearm length) of the same 67 individuals varied with reproductive condition but ranged from 0.460 to 0.952 ( Ober et al. 2017b). In Miami, BCI for E. floridanus was lower than that of individuals in a natural area in Charlotte County, but further research and a larger sample size is needed to determine if this is significant ( Ober et al. 2017b; Webb et al. 2021).

Eumops floridanus is active throughout the year and does not hibernate or have extended periods of torpor in the warm climate of Florida (FWC 2013). However, E. floridanus may become temporarily torpid during inclement weather (FWC 2013). For feeding, E. floridanus emits frequency-modulated echolocation calls typically between 10 and 18 kHz, with maximum frequencies of 16–22 kHz, which is lower than any other Florida bat ( Fig. 6 ; Bailey et al. 2017b) and is known to have a loud, audible call ( Barbour and Davis 1969; Robson et al. 1989; Best et al. 1997).

ONTOGENY AND REPRODUCTION

Eumops floridanus usually roosts in female-dominated harem groups of around 10 individuals with typically only one dominant, reproductively active male characterized by an open gular gland, greater mass, and larger testes compared to other males within the roost, although these observations are only from the western part of the distribution ( Belwood 1981; Ober et al. 2017a; Braun de Torrez et al. 2020). Pregnant females, nonvolant young, and juveniles are present from April through December; this relatively long breeding season suggests that E. floridanus is polyestrous ( Timm and Genoways 2004; Bailey et al. 2017a; Ober et al. 2017a). Pregnancy rates were higher in April than in August or December ( Ober et al. 2017a), and presumably most females give birth to only a single young each year (FWC 2013). Similarly, males had higher percentages of reproductive activity in April than in either August or December ( Ober et al. 2017a). Little is known about the length of gestation in E. floridanus or its close relatives, and because most reproductive studies have been conducted at one site in Charlotte County, much remains to be learned about breeding chronology elsewhere. A closely related species, the western mastiff bat ( E. perotis ), has an approximate gestation period of 80–90 days ( Ammerman et al. 2012), which is likely similar for E. floridanus .

Mean body mass (± SD) of 56 pregnant females was 47.13 ± 4.10 g ( Ober et al. 2017b). A pregnant female (UF 10923) found in a roost tree in Punta Gorda, Charlotte County in September of 1979 weighed 55.4 g and had one fetus with a crown-to-rump length of 23 mm ( Belwood 1981). The preserved fetus had a forearm length of 14 mm (UF 10923). An injured, pregnant female that was captured in 1988 in Coral Gables, Miami-Dade County, Florida had the following measurements (mm): total length 137, tail length 50, forearm length 63, and tragus length 4.5 ( Robson et al. 1989). This female later aborted a male fetus (UF 24317) that weighed 3.9 g and had a total length of 68 mm, crown-to-rump length of 38 mm, tail length of 22 mm, length of hind foot of 9 mm, forearm length of 21 mm, and ear length of 7 mm ( Robson et al. 1989).

Male reproductive condition is reflected in the external appearance of the gular glands. Males with open gular glands on average weighed more (open [n = 12; ¯x ± SD]: 45.7 ± 1.00 g; closed [n = 9]: 40.3 ± 1.47 g) and had increased average testes length (open [n = 11]: 7.9 ± 0.51 mm; closed [n = 4]: 5.7 ± 0.67 mm) compared to males with closed gular glands ( Ober et al. 2017a). Males with open gular glands also typically had descended testes, whereas those with closed gular glands often had abdominal testes ( Ober et al. 2017a). An adult male from the Punta Gorda roost had descended testes (7 and 9 mm, respectively) and weighed 46.6 g ( Belwood 1981). Eumops floridanus demonstrates resource-defense polygyny in which the dominant male spends significant time defending the roost to maintain access to females ( Braun de Torrez et al. 2020). Roosts (n = 12) in Charlotte County were active all year and were consistently occupied by dominant males more than nondominant males, indicating that dominant males likely sacrificed foraging time to protect the roost ( Braun de Torrez et al. 2020).

Figures

Fig. 2.—Close-up view of the face of Eumops floridanus from Charlotte County, Florida depicting the large, forward-pointing ears that join at the base and the smooth upper lip. Photograph by K. Smith (Florida Fish and Wildlife Conservation Commission) used with permission.

Fig. 3.—View of the gular gland and a hypopigmented marking on a male Eumops floridanus from Charlotte County, Florida. Photograph by J. Gore (Florida Fish and Wildlife Conservation Commission).

Fig. 4.—Dorsal, ventral, and lateral views of the skull and lateral view of the mandible of an adult male Eumops floridanus (UF [University of Florida, Florida Museum of Natural History mammal collection] 22379) from a private residence in Coral Gables, Miami-Dade County, Florida. Greatest length of skull is 21.54 mm. Photograph by V. Mathis.

Fig. 5.—Estimated geographic distribution of Eumops floridanus across counties in south Florida based upon recent occurrence records (visual and acoustic). Fossil sites are also depicted on the map.

Fig. 6.—A spectrogram of a Eumops floridanus search call recorded with a full spectrum Song Meter SM3BAT detector and an external SM3-U1 ultrasonic microphone and visualized with Kaleidoscope Viewer (Wildlife Acoustics, Inc., Maynard, Massachusetts) in compressed view (top) and in real time (bottom). Calls recorded by E. Braun de Torrez in Collier County, Florida, 2015 and used with permission.