Extinct West Indian Shrews (Nesophontidae)

views updated

Extinct West Indian shrews

(Nesophontidae)

Class Mammalia

Order Insectivora

Family Nesophontidae

Thumbnail description
Extinct shrew-like insectivores, known only from subfossil remains

Size
Species ranged from mouse-sized to chipmunk-sized

Number of genera, species
1 genus, at least 8 species

Habitat
Varied

Conservation status
All Nesophontidae species are considered Extinct

Distribution
Several islands of the Greater and Lesser Antilles

Evolution and systematics

The Nesophontid shrews comprise one family, Nesophontidae, one genus, Nesophontes, and eight species, namely: Puerto Rican nesophontes (Nesophontes edithae); slender Cuban nesophontes (Nesophontes longirostris); greater Cuban nesophontes (Nesophontes major); lesser Cuban nesophontes (Nesophontes submicrus); western Cuban nesophontes (Nesophontes micrus); Atalaye nesophontes (Nesophontes hypomicrus); Haitian nesophontes (Nesophontes zamicrus); and St. Michel nesophontes (Nesophontes paramicrus).

Present scientific knowledge places family Nesophontidae closest to the solenodons (family Solenodontidae), of which two species survive in Cuba and Hispaniola. Nesophontidae are also considered to be closely related to the more generalized shrew species of the family Soricidae, which they most physically resemble.

The scientific jury is still out on the exact origins of the Nesophontidae. One or more founder species may have rafted on vegetation to the Antilles from the mainlands of North or Central America, or they may have been carried along on dry land as plate tectonic movements separated the proto-Antilles Islands from Central America (vicariance). In either scenario, there may have been secondary colonization after the Antilles became an isolated archipelago; Nesophontidae species already on the Antilles may have rafted among some of these islands, colonized them, and produced new species.

Physical characteristics

Judging from skeletal remains, Nesophontidae closely resembled the more generalized species of the soricid shrews in appearance and morphology, with some minor variation due to isolation and adaptive evolution. Structurally, they departed little from the standard shrew body plan, except for size variations. All had typically long, narrow skulls, long and mobile snouts, perhaps more moveable than those of soricid shrews, small eyes, and a tail about as long as the body. Each of the four feet carried five fingers and five toes, each toe bearing a claw.

The exact body dimensions and weights of the Nesophontidae species can only be estimated, since their remains are merely skulls and isolated postcranial (non-skull) bones. Judging from these remains, Nesophontes edithae, the Puerto Rican nesophontes, was the largest species, with a skull length of up to 1.7 in (44 mm), a femur length of 1.0–1.1 in (27–28 mm), a head-body length of 6.3–7.5 in (160–190 mm) and an estimated living weight of 6.4–7.1 oz (180–200 g). It was about the size of a chipmunk or laboratory rat, although it probably had a more lithe build. N. zamicrus, the Haitian nesophontes, was the smallest species.

Hispaniola was home to three native species of Nesophontidae, large, medium-sized, and small. The largest species was about two-thirds the size of N. edithae, while the smallest was about the size of a large soricid shrew. There was a similar, size-ranked array of three nesophontid species on Cuba, the sizes about the same as those of the Hispaniolan species.

Evidence of sexual dimorphism was observed in skeletal remains of Nesophontes edithae, male skulls being larger than female, but size disparities could also be due to age differences. Nevertheless, the case for sexual dimorphism among the nesophontids has recently been reopened.

Distribution

The Caribbean/Antillean islands of Cuba, the Isle of Pines, Hispaniola, Ile de Gonave, Puerto Rico, plus the Grand Cayman Islands, home of two as yet unnamed species.

Habitat

Lowland and montane tropical forests.

Behavior

Behavior can only be surmised from skeletal remains, but is likely to have been similar to that of soricid shrews (Soricidae).

Feeding ecology and diet

Food habits and feeding habits are unknown, but judging by the teeth and morphology, the nesophontids were likely omnivorous, with some emphasis on animal food, mostly invertebrates, especially insects, as with soricid shrews. None of the Nesophontidae species developed any specialized or derived dentition as adaptations to new diets.

Reproductive biology

Nothing is known.

Conservation status

All known species of Nesophontidae are considered extinct. Most or all species of Nesophontidae were probably contemporaneous with man, including Native Americans and

the early European colonizers of the Antilles, the latter from a.d. 1500 onward.

There are no documented records of living nesophontid species. All that zoologists know about the genus and species is from skulls and scatted postcranial bones found in owl pellets. Some such pellets are found alongside other owl pellets containing bones of Old World rats and mice, indicating that some of the species were still alive when Europeans began colonizing the islands. Predation by and competition with Old World rats, along with extensive deforestation, probably brought about the extinction of the Nesophontidae.

There is a small possibility that a few nesophontid species may still survive. Fresh remains, in barn owl pellets, were found as recently as the 1930s in Haiti. Some of the bones retained bits of dried, yet fresh-looking, tissue. It was accordingly suggested that some species of Nesophontes might yet be extant. Nevertheless, more recent searches for living nesophontids by researchers in Hispaniola and Puerto Rico found no convincing evidence of survivors. More recently, researchers recovered some Nesophontes material from Cueva (cave) Jurg, Parque Nacional Sierra de Baoruco, Dominican Republic, that included a few hairs and tiny bits of dried tissue, but radiocarbon dating of the bone collagen estimates their age at about 700 years old.

Significance to humans

The Nesophontidae probably had little if any direct significance to either Native Americans or European colonists. There is no compelling evidence that Native Americans (or Europeans) used any of the nesophontid species for food. Like shrews in general, Nesophontidae lived secretive existences.

Resources

Books

Morgan, G. S. "Late Quaternary Fossil Vertebrates from the Cayman Islands." In The Cayman Islands: Natural History and Biogeography, edited by M. A. Brunt and J. E. Davies. New York: Kluwer, 1994.

Nowak, R. M., ed. "Family Nesophontidae (Extinct West Indian Shrews)." In Walkers Mammals of the World, 6th ed. Baltimore: Johns Hopkins University Press, 1999.

Whidden, H. P., and R. J. Asher. "The Origin of the Greater Antillean Insectivores." In Biogeography of the West Indies: New Patterns and Perspectives, edited by C. A. Woods and F. E. Sergile. Boca Raton, FL: CRC Press, 2001.

Periodicals

Alcover, J. A., A. A. Sans, and M. Palmer. "The extent of extinctions of mammals on islands." Journal of Biogeography 25 (1998): 913–918.

Anthony, H. E. "Mammals of Puerto Rico, living and extinct—Chiroptera and Insectivora." Scientific Survey of Puerto Rico and the Virgin Islands, New York Academy of Sciences 9, no. 1 (1925).

Choate, J. R., and E. C. Birney. "Subrecent Insectivora and Chiroptera from Puerto Rico." Journal of Mammalogy 49, no. 3 (1968): 400–412.

MacPhee, Ross, et al. "Radiometric dating and 'last occurrence' of the Antillean insectivore Nesophontes." American Museum Novitates 3264 (1999): 1–19.

McFadden, Bruce J. "Rafting mammals or drifting islands? Biogeography of the Greater Antillean insectivores Nesophontes and Solenodon." Journal of Biogeography 7 (1980): 11–22.

McFarlane, Donald A. "A note on dimorphism in Nesophontes edithae (Mammalia: Insectivora), an extinct island-shrew from Puerto Rico." Caribbean Journal of Science 35 (1999): 142–143.

Miller, G. S. "Three small collections of mammals from Hispaniola." Smithsonian Miscellaneous Collections 82, no. 15 (1930): 1–10.

Morgan, G. S., and C. A. Woods. "Extinction and zoogeography of West Indian land mammals." Biological Journal of the Linnaean Society 28 (1986): 167–203.

Whidden, H. P., and C. A. Woods. "Assessment of sexual dimorphism in the Antillean insectivoran Nesophontes." American Zoologist 40, 6 (2000): 1257.

Woods, Charles A., Jose A. Ottenwalder, and W. R. Oliver. "Lost mammals of the Greater Antilles." Dodo: Journal of the Jersey Wildlife Preservation Trust 22 (1985): 23–42.