Elephantuluselephant-shrews
Diversity
The genus Elephantulus is one of four genera of elephant shrews, or sengi (family Macroscelididae). There are 16 species of sengi, 11 of which are included in the genus Elephantulus. Sengis are small, have elongated rostrums, and closely resemble shrews (family Soricidae) both in appearance and behavior. However, sengis are part of the clade Afrotheria, meaning they are only distantly related to shrews and are more closely related to tenrecs (family Tenrecidae), golden moles (family Chrysochloridae), and even elephants (family Elephantidae). Sengis are endemic to Africa, are primarily insectivorous, and exhibit monogamous mating strategies.
More recently, genetic evidence suggests that species in the genus Elephantulus represent a paraphyly, and there are currently proposals to reclassify species into new genera. Namely, there is evidence that North African sengis (Elephantulus rozeti) are more closely related to four-toed sengis (Petrodromus tetradactylus) and should be reclassified as Petrosaltator rozeti. Other research indicates that Somali sengis (Elephantulus revoili) and rufous sengis (Elephantulus rufescens) belong to a newly proposed genus, Galegeeska. ("Family Macroscelididae", 2022)
Geographic Range
Sengis are native and endemic to the Ethiopian region. The majority of sengi species live in southern and south-central Africa, around or below the equator. However, 3 of the 11 species in the genus Elephantulus have disjunct populations in other regions of Africa. Somali sengis (Elephantulus revoili) and rufous sengis (Elephantulus rufescens) live in the African Horn, and North African sengis (Elephantulus rozeti) live in the Maghreb region in northwest Africa. (Panchetti, et al., 2008)
Habitat
Species in the genus Elephantulus inhabit a wide range of land cover types, including arid deserts, semi-arid grasslands, tropical and subtropical forests, and mediterranean areas. They build nests in covered areas, such as rocky outcrops or ground-level vegetation and leaf litter. Some species also maintain specific trails throughout their home ranges, which they travel along while foraging for food or escaping predators. Although sengis do not typically inhabit underground burrows, short-snouted sengis (Elephantulus brachyrhunchus) living in grasslands were observed using termite mounds as refugia during wildfires. Following the wildfires, short-snouted sengis shifted their foraging behavior from grassy areas to areas under shrubs and thickets. This demonstrates that at least some sengi species select foraging areas based on levels of vegetative cover, likely to decrease predation risk. (Yarnell, et al., 2008)
- Habitat Regions
- temperate
- tropical
- terrestrial
- Terrestrial Biomes
- savanna or grassland
- forest
- scrub forest
Systematic and Taxonomic History
There are 11 species in the genus Elephantulus: short-snouted sengis (Elephantulus brachyrhynchus), cape sengis (Elephantulus edwardii), dusky-footed sengis (Elephantulus fuscipes), dusky sengis (Elephantulus fuscus), Bushveld sengis (Elephantulus intufi), Somali sengis (Elephantulus revoili), North African sengis (Elephantulus rozeti), rufous sengis (Elephantulus rufescens), eastern rock sengis (Elephantulus myurus), western rock sengis (Elephantulus rupestris), and Karoo rock sengis (Elephantulus pilicaudus). Furthermore, there are two subspecies of North African sengis and six subspecies of rufous sengis. There is current disagreement on the phylogenic relationships within Elephantulus, as different analyses have yielded differing results. In 2008, Karoo rock sengis were distinguished from cape sengis based on genetic and morphological data. More recently, researchers have debated classifying North African sengis as members of a new genus, Petrosaltator, based on genetic evidence. Additionally, some researchers have argued that the genus Elephantulus is paraphyletic and have proposed that the genera Petrodromus and Macroscelides be subsumed into the genus Elephantulus to make a monophyly. ("Family Macroscelididae", 2022; Dumbacher, 2016; Panchetti, et al., 2008; Smit, et al., 2008; Smit, et al., 2011)
Physical Description
Sengi morphology, including the morphology of species in the genus Elephantulus, has remained relatively unchanged for around 20 million years, as evidenced by fossil records. They are small and usually have light brown or grey coloration. They have relatively large eyes and ears, and their hind feet are longer than their forefeet. The testes of males are located internally, posterior to their kidneys. Males have a long epididymis for storing sperm and a long penis, with the distal portion located externally, terminating near their sternum.
A study on cape elephant shrews (Elephantulus edwardii) caught in South Africa found that females were slightly larger than males, on average. The females have a combined head and body length of 111 mm and a tail length of 140mm, for a total length of 251 mm, on average. Males were slightly smaller, with an average overall length of 242 mm. Females also weighed more, with an average body mass of 57 g compared to an average of 48 g in males. For both sexes, the ear length was an average of 30 mm.
Species in the genus Elephantulus have two lower molars, similar to species in the genus Macroscelides, but Elephantulus species can be distinguished by the relatively small size of their tympanic bullae, a trait they share with species in the genus Nasilio. A study on western rock sengis (Elephantulus rupestris) found that populations at higher elevations had narrower, more elongated skulls, whereas populations at lower latitudes typically had shorter rostrums, larger tympanic bullae, and expanded occipital regions. It is likely that the populations at lower elevations faced greater predation pressure and thus have developed traits that improve predator detection, such as improved hearing and vision. (Rathbun and Rathbun, 2006; Scalici, et al., 2018; Stuart, et al., 2003; van der Horst, 1944; Woodall, 1995)
- Other Physical Features
- endothermic
- bilateral symmetry
- Sexual Dimorphism
- female larger
Reproduction
All species in the genus Elephantulus are socially monogamous and mate year round. Mating pairs establish shared territories, but spend little time in coordinated activities. However, males exhibit mate guarding behaviors when females enter estrus, actively defending their mates from intruding males.
Studies on rufous sengis (Elephantulus rufescens) have described brief sexual interactions between males and females. Females exhibit a behavior known as vaginal marking, wherein they secrete a chemical to signal that they are sexually receptive. Studies on short-snouted sengis (Elephantulus brachyrhynchus) found that females have 5 to 6 litters per year, with an average litter size of 1.6 offspring. This suggests that females have an average of 8.3 offspring per year. Sengis exhibit less reproductive activity during cold seasons, and populations at higher latitudes do not reproduce at all during the winter. Reproductive activity is typically highest during the wet season, although this differs depending on the regional environment. Sengis are precocial, and are capable of walking less than 4 hours after birth. (Lumpkin and Koontz, 1986; Neal, 1995; Rathbun and Rathbun, 2006; Stuart, et al., 2003)
- Mating System
- monogamous
Sengi species in the genus Elephantulus are monogamous, forming weak pair bonds. Males exhibit mate-guarding behavior, actively defending females from intruding males. However, sengis often have overlapping territories and, if males die, their mates may breed again with other males. The age at which sengis reach maturity is not well studied, and more research is needed to understand their reproductive development and behavior. (Rathbun and Rathbun, 2006)
- Key Reproductive Features
- iteroparous
- year-round breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- fertilization
Species in the genus Elephantulus exhibit limited parental investment. Bushveld sengis (Elephantulus intufi) have been described as having an “absentee system” of parental care, with mothers making short, infrequent visits to nurse their young. Males exhibit little direct parental care, but they spend approximately 40% of their time maintaining trails throughout their territories. The trail systems that sengis construct help them escape predation and access foraging space, and juveniles use the same trail systems as their parents. Newborn sengis are precocial, and are capable of standing and running less than 4 hours after birth. (Rathbun and Rathbun, 2006)
- Parental Investment
- precocial
- male parental care
- female parental care
-
pre-hatching/birth
-
protecting
- male
-
protecting
-
pre-weaning/fledging
-
provisioning
- female
-
provisioning
Lifespan/Longevity
There is limited information regarding the longevity of species in the genus Elephantulus. A cape sengi (Elephantulus edwardii) was reported to live up to 5.7 years old in captivity, but more research is needed to determine the typical lifespans of wild sengis. (Weigl, 2005)
Behavior
Sengi species in the genus Elephantulus are mostly diurnal, but some species are partially crepuscular or nocturnal. Sengis avoid the hottest parts of the day, only leaving shady areas to catch nearby prey. In general sengis will travel longer distances compared to rodent species (order Rodentia) in the same environments. Sengis are cursorial and saltatorial. They have long hind legs that allow them to run at speeds up to 28 km/h. Sengis are generally solitary, but exhibit monogamous mating behavior and often have territories that overlap with neighboring sengi territories. Sengis perform scent marking to communicate their sexual status and have been observed to interact with conspecifics by touching their noses together. Sengis are prey animals and exhibit a high level of vigilance when they are active and when they are resting. When they feel threatened, they will perform foot-drumming behaviors or flee along trail systems that they maintain throughout their territory. Sengis typically establish shelters underneath low vegetation or between large rocks, but most species do not use nesting material.
The thermoregulatory behavior of sengis in the genus Elephantulus has been relatively well studied. More specifically, their use of torpor has been studied extensively. For example, cape sengis (Elephantulus edwardii) that live at high elevation frequently employ torpor, reducing their metabolism and body temperature to conserve energy especially during times of the year with low ambient temperatures. Other species in the genus Elephantulus at lower elevations also use torpor more often during cold seasons than warm seasons. Because sengis are small-bodied mammals, they lose heat more rapidly to their environment, so using torpor is an important strategy in reducing daily energetic demands. Sengis also exhibit basking behaviors during sunny weather, likely as another strategy to reduce the energy they use on maintaining high body temperatures. (Geiser and Mzilikazi, 2011; Lovegrove and Mowoe, 2014; Rathbun and Rathbun, 2006; Scalici, et al., 2018)
- Key Behaviors
- cursorial
- terricolous
- saltatorial
- diurnal
- crepuscular
- motile
- sedentary
- daily torpor
- territorial
Communication and Perception
There is limited information regarding the methods of communication used by species in the genus Elephantulus. They have large eyes and ears and long snouts, so they likely rely on a combination of visual, acoustic, and chemical stimuli to perceive their environment. Sengis exhibit scent marking behaviors, which likely serves as a method of intraspecific communication, relaying information about territorial boundaries and sexual receptivity. They also use foot drumming when they encounter unfamiliar conspecifics or potential predators. Foot drumming may be a visual signal of distress or it may produce vibrations in the ground that deter predators. The functions of such behaviors are not well studied, and more research is needed to fully understand the communication methods of species in the genus Elephantulus. (Rathbun and Rathbun, 2006)
Food Habits
Sengi species in the genus Elephantulus are predominantly insectivorous. They make daily movements along their trail systems and glean insects from vegetation or the ground. The specific types of insects that sengis consume varies depending on geographic location.
A study on eastern rock sengis (Elephantulus myurus) found that they preferred to forage in areas with rocks and pebbles as opposed to areas with sand or sawdust. Eastern rock sengis used their snouts and long tongues to detect and collect food, a behavior that is likely similar to the foraging methods of other members of the genus Elephantulus. The diets of cape sengis (Elephantulus edwardii) consist primarily of ant species. It is likely that other species in the genus Elephantulus also eat ants, but they may also opportunistically eat other insect species along their trail systems. Some Elephantulus species are not strictly insectivorous. For example, a study on the stomach contents of short-snouted sengis (Elephantulus brachyrhynchus) found a high proportion of plant material in addition to insect species. (Leirs, et al., 1995; Mohammad and Brown, 2011; Scalici, et al., 2018; Stuart, et al., 2003)
Predation
There is limited information regarding specific predators of sengis in the genus Elephantulus, and more research is required to identify the organisms that prey on Elephantulus species. However, it is well understood that many sengi species maintain trail systems throughout their territories. They regularly move through these trail systems and remove any obstacles obstructing the paths. These trail systems benefit sengis when threatened by predators, as they can make rapid escapes along unobstructed paths. Most sengi species in the genus Elephantulus have dull brown or grey coloration, which helps them camouflage with their environment. Furthermore, they spend most of their time near ground cover, such as vegetation and large rocks, which reduces the chances of being detected by potential predators. (Rathbun and Rathbun, 2006)
Ecosystem Roles
Despite the wide range of environmental conditions in which Elephantulus live, they have relatively similar life history traits, including morphology, social behavior, and diet. They prey on insects and occasionally plants, and they serve as prey for other species in their communities. Beyond their roles as predators and prey, relatively little is known about the roles that sengis play in the ecosystems they inhabit. (Rathbun and Rathbun, 2006)
Economic Importance for Humans: Positive
Species in the genus Elephantulus have no known positive economic impacts, though more research is needed to fully understand their ecosystem roles.
Economic Importance for Humans: Negative
Species in the genus Elephantulus have no known negative economic impacts, though more research is needed to fully understand their ecosystem roles.
Conservation Status
According to the IUCN Red List, there are only two sengi species in the genus Elephantulus that have stable populations and are of least concern: rufous sengis (Elephantulus rufescens) and eastern rock sengis (Elephantulus myurus). There are five other species that are also of least concern, but their population trends are unknown: short-snouted sengis (Elephantulus brachyrhynchus), Bushveld sengis (Elephantulus intufi), western rock sengis (Elephantulus rupestris), North African sengis (Elephantulus rozeti), and cape sengis (Elephantulus edwardii). The other four species in the genus Elephantulus are considered data deficient on the IUCN Red List, so their population status and conservation needs are unknown: Karoo rock sengis (Elephantulus pilicaudus), dusky sengis (Elephantulus fuscus), dusky-footed sengis (Elephantulus fuscipes), and Somali sengis (Elephantulus revoilii).
There are no known conservation efforts in place for sengis specifically. However, some species in the genus Elephantulus have geographic ranges that extend into areas established to protect wildlife, such as national parks. ("IUCN Red List", 2022)
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- IUCN Red List [Link]
- Not Evaluated
Contributors
Justin Arndt (author), Colorado State University, Galen Burrell (editor), Special Projects.
Glossary
- Ethiopian
-
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
- bilateral symmetry
-
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- carnivore
-
an animal that mainly eats meat
- chemical
-
uses smells or other chemicals to communicate
- crepuscular
-
active at dawn and dusk
- diurnal
-
- active during the day, 2. lasting for one day.
- endothermic
-
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
- female parental care
-
parental care is carried out by females
- fertilization
-
union of egg and spermatozoan
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- insectivore
-
An animal that eats mainly insects or spiders.
- iteroparous
-
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
- male parental care
-
parental care is carried out by males
- monogamous
-
Having one mate at a time.
- motile
-
having the capacity to move from one place to another.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- omnivore
-
an animal that mainly eats all kinds of things, including plants and animals
- saltatorial
-
specialized for leaping or bounding locomotion; jumps or hops.
- scrub forest
-
scrub forests develop in areas that experience dry seasons.
- sedentary
-
remains in the same area
- sexual
-
reproduction that includes combining the genetic contribution of two individuals, a male and a female
- tactile
-
uses touch to communicate
- temperate
-
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
- terrestrial
-
Living on the ground.
- territorial
-
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- tropical savanna and grassland
-
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
- savanna
-
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
- temperate grassland
-
A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
- year-round breeding
-
breeding takes place throughout the year
- young precocial
-
young are relatively well-developed when born
References
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