Solenodons

(Solenodontidae)

Class Mammalia

Order Insectivora

Family Solenodontidae

Thumbnail description
A rabbit-sized insectivore with shrew-like features

Size
Up to 2.4 lb (1,100 g)

Number of genera, species
1 genus; 2 extant species

Habitat
Tropical moist montane forests

Conservation status
Endangered: 2 species

Distribution
Caribbean/Greater Antilles islands of Hispaniola and Cuba

Evolution and systematics

The relationships among the numerous insectivore species is far from settled. Evolutionary biologists have not settled the question of whether the families listed within the order Insectivora are monophyletic (sharing a common ancestor species) or polyphyletic (deriving from several separate origins). Presently, the solenodontids appear to be most closely related to several species of extinct shrews, the Nesophontidae, native to various islands of the Antilles, while both families share similarities among the family Tenrecidae (the tenrecs of Madagascar and mainland Africa) and the subfamily Potamogalinae (otter shrews of mainland Africa).

The Solenodontidae show an array of primitive mammalian features, but whether they represent a relict family from the mainlands, little changed, or are the derived descendants of smaller colonizing insectivores that evolved to "giant" size on the islands, is not clear. These ancestors most likely rafted on vegetation from the mainlands of the Americas to Cuba and Hispaniola as long ago as the Mesozoic and early Cenozoic eras. The Solenodontidae survived on the islands without competition from more advanced mammal types.

Solonodontidae contains the living genus Solenodon; two living species, the Hispaniolan or Haitian solenodon, S. paradoxus, in Hispaniola, and the Cuban solenodon or "almiqui,"S. cubanus, in Cuba. Also included in this family are two recently extinct (late Pleistocene to present) species, Marcano's solenodon, S. marcanoi, in Hispaniola, and Arredondo's solenodon, S. arredondoi, in Cuba.

Physical characteristics

At first glance, a typical solenodon resembles a rabbit-sized shrew, with a shrew's characteristic long, conical, whiskerstudded snout, even more pronounced in the solenodon. Cuban solenodons are slightly smaller, on average, than Hispaniolan solenodons. An adult Hispaniolan solenodon can weigh up to 2.4 lb (1,100 g), its combined head and body length can reach 15 in (39 cm) and the tail length, 8 in (21 cm). An adult Cuban solenodon's maximum weight is 1.7 lb (800 g), and its maximum head and body length is 14 in (36 cm). The extinct Solenodon arredondoi was much larger. Its weight, based on fossil remains, has been roughly estimated at 3.3–4.4 lb (1,500–2,000 g), and its head and body length at

18–22 in (45–55 cm). There is no sexual dimorphism in the living species of solenodon (i.e., no differences between the sexes in size, shape, or coloration).

The solenodons show a puzzling mix of primitive and derived traits. Among the primitive characters are a poisonous bite and the ability to echolocate. Solenodon sight is poor, but hearing, olfactory, and tactile senses are acute. Derived

traits include longevity, low birth frequency, low number of young per litter, and the os proboscis bone in the Hispaniolan solenodon.

The eyes are tiny and shrew-like. The large ears partially protrude from the fur. The legs are relatively long, and well-muscled. Each of all four paws carries five digits with large, strong claws.

The fur is dense, coarser in the Hispaniolan solenodon, finer and softer in the Cuban solenodon. Fur color in S. paradoxus ranges from brown through reddish brown to yellowish brown on the upper, dorsal body, with a lighter underside. The fur of S. cubanus varies from dark brown to black, with a white or yellowish face, snout, and shoulders. The forehead in both species is sparsely covered with hair, while the ears, legs, snout, and scaly, rat-like tail are nearly hairless. The snout sprouts long vibrissae, or sensory whiskers, along its length.

Individuals of both species carry scent glands in the armpits and groin. In females, the two mammae are located in the inguinal (groin) region. In males, the penis, except during mating, and the testes are carried within the abdominal cavity.

In all individuals of both species, the lower second incisors are grooved to channel poison. The name solenodon, meaning "slotted tooth," is based on this feature. The grooves connect with a duct that supplies a poisonous neurotoxin from glands below the incisors. Some species of shrews carry similar modified teeth and poison.

Distribution

Caribbean/Greater Antilles islands of Hispaniola and Cuba.

Habitat

Tropical montane forest; also brush country and near plantations.

Behavior

Both species are nocturnal, hiding and sleeping during the day in hollows or burrows. Adults are solitary in their foraging, although several individuals may shelter together.

Solenodons are easily startled, especially by sharp or high-pitched sounds, and are easily provoked into scrappy rages against other solenodons or other animal species. Given its jaw full of sharp teeth, modeled according to the shrew pattern with some modification, an enraged solenodon can deliver a severe bite.

Solenodons have long life spans and low reproductive rates, unusual in so small an animal. One captive Hispaniolan solenodon lived for eleven years, while a captive Cuban solenodon lived for five years. Insectivores rarely live longer than a couple of years.

Individuals walk in a winding course, holding the tail level. When alarmed, a solenodon can run in a straight line, with some speed, but will more likely run off in an erratic pattern. Solenodons can climb, but seldom do so. When sitting up or scratching itself, a solenodon uses its tail as a prop.

Solenodons produce a variety of vocalizations, including wheezing, snuffling, grunting, squeaking, and shrieking.

Feeding ecology and diet

Solenodons are generalist feeders with some emphasis on insects and spiders. When foraging, a soledonon takes a winding course using its flexible snout to root in dirt and poke into leaf litter and cracks. A soledonon uses smell and tactile senses to find earthworms, arthropods, and snails, digging them out of the soil or snagging them in leaf litter or tight spaces in rock and wood. It also uses its powerful fore-limbs and claws to tear into soft, rotten wood in search of resident edibles.

Reproductive biology

A female gives birth to a litter of one to three young, and can birth two litters within a year. The mother bears only two teats, situated ventrally near the groin. The young are weaned after 75 days, although they may remain with the mother while subsequent litters are born and raised.

Apparently, males are always able to breed, since they will attempt copulating with females at any time, while females go in and out of estrous according to no strict pattern. Courting behavior is similar to insectivores in general, with scent-marking and mutual sniffing. May be polygamous or promiscuous.

Conservation status

Both solenodon species are listed as Endangered by the IUCN. Both species were written off as extinct in the early twentieth century, but were subsequently rediscovered. Ironically, solenodons are among a mere handful of surviving mammal species among a large and varied array of recently

extinct native mammals in the Antilles, including rodents, New World monkeys, sloths, and other insectivores.

Solenodons are threatened by deforestation, predation by introduced animals, and killing by humans who consider them pests.

Significance to humans

Rural people in Hispaniola frequently kill solenodons, blaming then for eating crops, although most likely the solenodons do not eat crops but damage them while grubbing for insects. In Cuba, the remaining solenodons are too remote from settled humanity to pose any sort of threat. Solenodons are not hunted for food in Hispaniola or Cuba.

Species accounts

List of Species

Hispaniolan solenodon

Solenodon paradoxus

taxonomy

Solenodon paradoxus Brandt, 1833, Dominican Republic.

other common names

English: Haitian solenodon; French: Solénodonte d'Haiti; German: Dominikanischer Schlitzrüssler, Haiti-Schlitzrüssler; Haitian French: Nez longue; Spanish: Solenodonte haitiano.

physical characteristics

Individuals resemble very large shrews. An adult weighs up to 2.4 lb (1,100 g). Its combined head and body length ranges 11–12 in (28–32.5 cm), and the tail length is 7–10 in (17.5–25.5 cm). There are five fingers and five toes, for, respectively, the forepaws and hind-paws, and all digits are equipped with large, strong claws, although the forelimbs are more powerfully muscled than the hindlimbs, and the forepaws are bigger. The underfur is short and dense, overlain by a coarser secondary coat. The forehead is sparsely covered with hair, while the ears, legs, snout, and scaly, rat-like tail are nearly hairless. The snout sprouts long vibrissae, or sensory whiskers, along its length.

Fur color ranges from brown through reddish brown to yellowish brown on the upper, dorsal body, with a lighter shade on the underside. A light-colored, roughly rectangular spot in the fur of the nape changes slightly in size and shape throughout the animal's life.

A signature characteristic of Solenodon paradoxus is the os proboscis, a small, round bone, located at the tip of the rostrum (bones of the nasal region), and which holds the proximal end of the cartilaginous support for the long snout. The os proboscis articulates with the rostrum in a ball-and-socket joint, a most unusual feature among the vertebrates. The Cuban solenodon lacks this feature.

distribution

The Caribbean island of Hispaniola; in the Dominican Republic, in several forested areas; in Haiti, only in the extreme southwest.

habitat

Montane tropical rainforest. The animals may sometimes settle in scrub, or near plantations.

behavior

The Hispaniolan solenodon forages nocturnally, hiding and sleeping during the day in spaces between rocks, in hollow trees, or in networks of burrows that the animals excavate. Usually, several individuals rest together in a hollow or burrow. Captive Hispaniolan solenodons will sleep piled in heaps within their shelters.

Wild male adults, and female adults without young, are solitary when foraging, even if they share burrow space.

Field researchers have often found collections of snail shells in the burrows of wild Hispaniolan solenodons. Captive solenodons have been observed collecting similarly small, hard objects, such as coarse chunks of peat moss and beechnut husks, and dragging them into their sleeping enclosures.

Captive solenodons show nesting activity, lining their sleeping shelters with hay, dried leaves, peat moss, and similar materials, pushing it into little heaps with their forepaws, then dragging it, backwards, with forepaws or jaws, into the nest enclosure. A pregnant female will prepare a litter nest.

Hispaniolan solenodons, in the wild or in captivity, produce a variety of vocalizations: wheezing and snuffling like hedgehogs, grunting like pigs, squeaking like guinea pigs, twittering like mice, and whimpering like young kittens. An excited or alarmed solenodon will sound off with penetrating shrieks. Mothers and their young, or mates, make bird-like contact calls, while courting individuals make repeated "piff" noises.

Hispaniolan solenodons appear to echolocate. An individual will produce a series of high-pitched clicks when checking out a new area or encountering a strange animal. Several species of shrew (Soricidae) and tenrecs use echolocation.

Sudden high, shrill, or sharp noises will panic the animals and send them fleeing. If threatened by a rival solenodon or another species, the solenodon will first take an upright, defensive posture and warn its opponent with a loud "chirp." If fleeing the opponent is the chosen option, a Hispaniolan solenodon first runs in an erratic pattern, then crouches motionless and hides its head. This behavior may have given it a survival edge against predators, particularly birds of prey, before human settlement of Cuba and Hispaniola, but those traits work against it when dealing with introduced predators like dogs, cats, and mongooses.

feeding ecology and diet

Hispaniolan solenodons are omnivorous, generalist feeders with some emphasis on insects and spiders, while varying their fare with worms, snails, small reptiles, roots, fruits, and leaves.

A Hispaniolan soledonon forages along an erratic, winding course, probably in accordance with a food-search pattern, while using its flexible snout to root in dirt and poke into leaf litter, using smell and tactile senses to find earthworms, arthropods, or land snails, digging them out of the soil or snagging them in leaf litter. A solenodon will carefully clean the dirt from a snagged earthworm with its front paws before eating it. The animal also uses its powerful forelimbs and claws to tear into soft, rotten wood in search of resident edibles.

Hispaniolan solenodons drink water by lapping it up with their tongues, while holding the snout bent upward, then swallow it while throwing their heads back.

reproductive biology

Mating behavior is common to insectivores, presumably polygamous or promiscuous. In captivity, a male introduced into a female's cage explores, and scent-marks by rubbing his anogenital area over objects and spots in the cage, often in areas already scent-marked by the female. As the two move closer to each other, they repeatedly make reassuring "piff" noises. Physical contact begins with nose-to-nose touching, followed by the two animals sniffing different parts of each other's body. As the male mounts, he secures his and the female's position by a neck grip on the female.

Both sexes of the Hispaniolan solenodon exude a greenish, oily fluid from scent glands in the armpits and groin. However, the amount of a female's excretions may indicate the level of arousal, while the male that can mate at any time excretes a similar fluid at a constant rate.

A female gives birth to a litter of one, two, or even three young in a nesting burrow, and she can birth two litters within a year. There is no set mating season. A mature Hispaniolan solenodon female's estrous lasts about a day, with intervals of nine to thirteen days between estrous periods. The gestation period is unknown. Individual young weigh 1.4–1.9 oz (40-55 g) at birth, and are blind and nearly hairless, although they've grown a complete coat of fur by two weeks after birth.

The female has two teats, situated near the groin. Out of a litter of three, one will probably die, since the mother can nurse only two at a time. When seven weeks old, the nursing youngsters accompany the mother outside in her foraging by hanging fast to her teats with their jaws, being dragged along wherever she goes. This behavior, known as "teat transport," is well known among rodent species, but among the insectivores, known only in solenodons. The young are weaned after 75 days, a long time for insectivores, while the young may sometimes remain with the mother while she births and raises sub-sequent litters. Males do not share in parenting.

conservation status

The Hispaniolan solenodon is listed as Endangered by the IUCN. The species is beset by deforestation, killing by humans who consider them pests, and by introduced house cats, dogs, and mongooses, against which the animals have little defense.

Hispaniolan solenodons sometimes nest and burrow near plantations, where the soil, made softer and more pliable by farming, makes for easier burrowing, while the plantations themselves are abundant with insects. Farmers kill solenodons, accusing them of attacking crops, when most likely the animals were foraging for insects in the fields, while the proximity to settled areas renders solenodons more vulnerable to harm from humans and introduced animals.

By 1907, the Hispaniolan solenodon had been written off as extinct, but several isolated populations have been rediscovered in Hispaniola. Of the two Hispaniolan nations, Haiti and the Dominican Republic, a 1996 survey found S. paradoxus in both countries, although its survival isn't likely in Haiti, which has been all but completely deforested.

significance to humans

Negatively, solenodons are considered only minor nuisances when they disturb agricultural land. There are not many of them, and they are not hunted for food. They are of no direct positive significance to humanity, but more abstractly, they are conservation symbols and living studies in the evolution of primitive placental mammals and in adaptive evolution on islands.

Resources

Books

Eisenberg, John F. "Tenrecs and Solenodons in Captivity." In International Zoo Yearbook 15. London: Zoological Society of London, 1975.

Ottenwalder, Jose. "Systematics and Biogeography of the West Indian Genus Solenodon." In Biogeography of the West Indies: Past, Present, and Future, edited by Charles Woods. Gainesville, FL: Sandhill Crane Press, 1989.

Woods, C. A., and F. Sergile, eds. Biogeography of the West Indies: Patterns and Perspectives, 2nd ed. New York: CRC Press, 2001.

Periodicals

Eisenberg, John F., and Edwin Gould. "The Behavior of Solenodon paradoxus in Captivity with Comments on the Behavior of other Insectivora." Zoologica 51 (1966): 49–57.

MacFadden, B.J. "Rafting Mammals or Drifting Islands?: Biogeography of the Greater Antillean Insectivores, Nesophontes and Solenodon." Journal of Biogeography 7 (1980): 11–22.

McDowell, S. B., Jr. "The Greater Antillean Insectivores." Bulletin of the American Museum of Natural History 115 (1958): 113–214.

Morgan, Gary S., and Jose A. Ottenwalder. "A New Extinct Species of Solenodon (Mammalia, Insectivora, Solenodontidae) from the Late Quaternary of Cuba." Annals of the Carnegie Museum 62 (1993): 151–16.

Patterson B. D. "An Extinct Solenodontid Insectivore from Hispaniola." Breviora 165 (1962): 1–11.

Woods, Charles A. "The Last Endemic Mammals in Hispaniola." Oryx 16 (1981): 146–152.

Organizations

IUCN—The World Conservation Union. Rue Mauverney 28, Gland, 1196 Switzerland. E-mail: [email protected] Web site: <http://www.iucn.org>

The Nature Conservancy of the Dominican Republic. 4245 North Fairfax Drive, Arlington, VA 22203-1606 USA. Phone: (703) 841-4878 or (800) 628-6860. E-mail: [email protected] Web site: <http://nature.org/wherewework/caribbean/dominicanrepublic/>

Other

Animal Diversity Web. [17 March, 2003]. <http://animaldiversity.ummz.umich.edu>.

The Shrew Site. [17 March 2003]. <http://members.vienna.at/shrew>

2002 IUCN Red List of Threatened Species. [17 March 2003]. <http://www.redlist.org>.

Walker's Mammals of the World (Online). Nowak, R. M. "Solenodons (Solenodontidae)." 1999 [17 March 2003]. <http://www.press.jhu.edu/books/walkers_mammals_of_the_world/insectivora.solenodontidae.solenodon.html>.

World Wildlife Fund Global 200 Ecoregions. "Greater Antillean Moist Forests." [17 March 2003]. <http://www.panda.org/resources/programmes/global200/pages/regions/region037.htm>.

World Wildlife Fund Global 200 Ecoregions. "Hispaniolan moist forests." [17 March 2003]. <http://www.worldwildlife.org/wildworld/profiles/terrestrial_nt.html>.

Kevin F. Fitzgerald, BS