Amblysomus

Diversity

African golden moles ( Amblysomus ) is a genus within the golden mole family ( Chrysochloridae ) comprised of five species, seven subspecies, and two cryptic species. Inhabiting the South African savannah and grasslands, these small mammals rely on their fossorial behaviors, prominent foreclaws, and cryptic coloration to avoid predators and endure harsh desert conditions. Golden moles hunt insects and other invertebrates by burrowing through soil and sand.

Geographic Range

In the family Chrysochloridae , sister taxa of Amblysomus are native to Africa, but the entirety of the Amblysomus genus is endemic to the southernmost region of Africa. Species within this genus such as Amblysomus marleyi and Amblysomus hottentotus have large habitable, coastal ranges in comparison to Amblysomus septentrionalis who have minimal mountain ranges to inhabit. Similarly to the features of a small range, Amblysomus robustus who has an extensive distribution and, in turn, has very low populations in each range contributing to their inconsistent geographic patterns. Unfortunately concerning their conservation status, two species Amblysomus robustus and Amblysomus septentrionalis have been notably observed in gardens and recreational areas specifically golf courses.

• Biogeographic Regions
• ethiopian ethiopian
  • native native

Habitat

The most inhabitable regions for Amblysomus include grasslands and mountain ranges in and around southern Africa. Migratory patterns show that some species inhabit more dense forest ranges in temperate areas. Despite these habitat preferences, conservation studies display an increased density of golden moles in recreational areas such as golf courses, gardens, and commercial farms. Conservation efforts are in order to understand the necessary migratory patterns to avoid urban expansion. Amblysomus septentrionalis is one species named for its specified habitat range, High-veld grasslands, typically with moist and sandy soils. Soft soils and silts are necessary for the fossorial behaviors of Amblysomus and in turn their survival. Golden moles use a double-tiered burrowing system with an upper foraging chamber and a lower nesting chamber. Despite these fossorial behaviors, some species inhabit higher elevations around 1800m while others inhabit the coastal regions of Cape Town.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest
• mountains mountains

• Wetlands
• marsh marsh

• Other Habitat Features
• suburban suburban
• agricultural agricultural

Systematic and Taxonomic History

The golden mole family, Chrysochloridae , includes the Amblysomus genus. The relation involves a common ancestor who had generations of branching in Chrysochloris that extended into Amblysomus as they evolved. Parsimony analyses with Bayesian models show that the similar morphology of all the genera and species still constitute monophyletic clades. These monophyletic clades include a division of chrysochlorids into amblysomines and chrysochlorines that resulted in two intermediate species, Neamblysomus and Chlorotalpa . Due to these intermediate species, Chlorotalpa is the closest relative of the Amblysomus species.

Physical Description

Amblysomus are very small, oval-bodied, and short-haired with a wide range of pelage colorations with clear patterns of countershading. Amblysomus robustus displays this most prominently with dark reddish-brown fur that fades into a pale orange on its ventral side, extending to its face and cheeks. In most species of adult golden moles, displays of sexual dimorphism in terms of size and weight are common, where males measure approximately 114-135mm compared to females who measure around 105-145mm at a body mass of 52-86g. Amblysomus robustus has been shown to be the largest in the golden mole family with the size differences correlating to inhabiting higher altitudes at lower temperatures. The most obvious differing external characteristic is the prominence of the fore-claw, largest in Amblysomus robustus and smallest in Amblysomus hottentotus longiceps , a subspecies of Amblysomus hottentotus . The adaptations of their fore-claws, short, dense fur, and absent eyes are due to the importance of their fossorial lifestyle. In addition, their fur coloration has proved to be an important adaptation for predator avoidance. To support these adaptations, golden moles are plantigrade in their hind feet and digitigrade on their forefeet due to their prominent fore-claws. The skull displays sexual dimorphism where the males have a larger skull and a narrower palate. Dentition is fairly constant among Amblysomus with zalambdodont dentition including adaptations such as molar talonids and an absent M3.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes shaped differently

Reproduction

Courtship behaviors are very aggressive from both the male and female and do not include the typical attraction behaviors. Since golden moles are entirely blind, females rely on penis size relative to body size to choose a reproductively successful mate. They may also utilize chirruping and foot stomping to attract or signal the female of a mate. Male golden moles chase and molest the smaller females as they are entirely solitary from members of the same genus. Amblysomus display a polygynandrous mating system because the males do not invest in parental care. The lack of male parental care decreases their energy expenditure and increases their reproductive success.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Due to the solitary nature of golden moles, the females provide all the care for offspring after birth. As in most mammals, Amblysomus are altricial with small litters of 1-3 young each breeding period. They are not seasonal breeders but breeding periods tend to increase in the wet summer months. The female provides a high investment in their young and delivers milk via two teats. The length of maternal care is dependent on when the offspring reaches adult size and maturity (35-45g), spanning approximately 45 days. Since this time is quite short, Amblysomus are polyoestrous mammals and may produce 10-12 offspring each year. In some species, the female may become pregnant while still weaning their previous litter to increase reproductive output. These offspring are hairless at birth with soft fore-claws and poor coordination that will require post-natal provisioning via the mother.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous
• embryonic diapause embryonic diapause

The reproductive behaviors of Amblysomus are poorly studied, but their daily behaviors are similar to their courtship behaviors. Since Amblysomus are solitary and territorial, courtship is very aggressive as males often chase and molest the female. This interaction often ends fatally for female golden moles. If the courtship interaction is successful, the female assumes the entire parental investment, including post-natal care and development. Amblysomus live in underground burrows, with a chamber dedicated to the brooding of offspring. In this chamber, the mother will gestate and birth her offspring while continuing care for roughly 45 days postpartum. Unfortunately, due to their solitary underground behaviors, the gestation length is unknown.

• Parental Investment
• altricial altricial
• female parental care female parental care
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

The lifespan of all species in the Amblysomus genus is unknown due to a lack of research funding and the inability to track them due to their fossorial behavior. Golden moles are also quite trap-shy making it extremely difficult to study them in captivity. It is known that deforestation and urbanization are the top two ecological risks for Amblysomus and have posed related risks such as predation via domestic animals (house pets).

Behavior

Amblysomus are entirely solitary animals and very aggressive towards members of their own species. The exception being Amblysomus hottentotus who has shown to display a symbiotic relationship with mole rats ( Heterocephalus graber ). The two species don't have competing diets and reduce energy investment by utilizing the same burrow. On the rare occurrence that they leave their burrow, they do so with the help of their large fore-claws and plantigrade hind feet to push themselves above ground. Golden moles display nocturnal behaviors and process daily torpor from dawn to late afternoon. Kuyper proposed that this daily torpor may not be due to gradual temperature changes and instead dependent on the abundance of invertebrates available. Daily torpor allows for the golden moles to conserve energy by regulating a lower metabolism in their torpor state. The seasons affect these subterranean animals as they are above ground more in the wet, summer months than the winter months. The burrowing systems of Amblysomus also correlate to these winter and summer seasons as the soil changes with the weather. In the colder months, golden moles spend more time constructing their burrows, the majority of which include separate sleeping, mating, and eating chambers. In the warmer months, the soil is much softer so burrowing becomes much easier, causing them to be much larger during these wet months. Despite the solitary status of these animals, a single burrowing system has been seen to be constructed by both male and female moles. In terms of predation and nutrition, Amblysomus has interesting habits. Golden moles are insectivores with a partial opportunistic diet including snails and slugs. When invertebrates are in low abundance, Golden moles may rely on carnivorous habits for nutrition. Oftentimes, they will resort to daily torpor so that invertebrates may accumulate in their burrow, rather than "hunting". In their natural environment, Amblysomus rarely drink or require water while in captivity, they do. They are able to do this because of their metabolism suppression capabilities and renal function efficiency.

• Key Behaviors
• fossorial fossorial
• nocturnal nocturnal
• motile motile
• sedentary sedentary
• daily torpor
• solitary solitary
• territorial territorial

Communication and Perception

Golden moles are entirely blind so they rely on tactile, chemical, and acoustic communication to perceive their environment. All of the listed senses have been adapted for prey and predator perception but vibrational communication is most advantageous. In terms of mating, Amblysomus use vocalization like chirruping, and foot stomping as a signal that they are ready to mate. The foot stomping displays a sense of seismic signaling as golden moles may easily perceive them. Amblysomus hottentotus has even been recognized hitting its head against the walls of the burrow to produce a longer-distance signal. This seismic signaling has only been studied in Amblysomus hottentotus in captivity but is established in many fossorial mammal lineages. Similarly to other fossorial animals, Amblysomus have enlarged malleus bones in their ears which heightens sensitivity to vibrations and sounds. The solitary nature of these animals leads to limited dominance/social hierarchies. Dominance may be displayed via overtaking neighboring burrows in more fertile soil. The criteria of this dominance is unknown but may be due to body size or burrow size.

• Communication Channels
• tactile tactile
• acoustic acoustic

• Other Communication Modes
• vibrations vibrations

• Perception Channels
• tactile tactile
• acoustic acoustic
• vibrations vibrations
• chemical chemical

Food Habits

Golden moles have a very efficient way of foraging for food. Digging below the surface but above their burrow allows for an accumulation of subsurface insects as well as protection. All Amblysomus species are insectivores with their typical diet consisting of Lumbricus terrestris , Gryllus campestris , and other insect larvae. In some cases, Amblysomus hottentotus have opportunistically fed on Gastropods, such as snails and slugs as well as plant material. Surprisingly, golden moles have adapted to their climate so well that the majority of species do not require water. Instead of directly drinking water, Amblysomus acquire water via ingesting their prey. Captive Amblysomus species displayed different diet preferences than those in the wild. Instances have been shown of golden moles eating garlic, potatoes, and species of lilies, Zantedeschia and Homeria . These observations are uncommon and do not occur in their natural habitat.

Depending on the size of the prey, golden moles hold the insect in their foreclaws and take it to an allocated chamber in the burrow. Once taken into the burrow, Amblysomus consume their prey with their typical mammalian dentition which allows for a grinding and shearing action of their prey. Especially for insectivores, sharp and grinding teeth are advantageous to break down the invertebrate exoskeleton.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore
• omnivore omnivore

Predation

Due to the small size of Amblysomus , 120-170 mm, fossorial adaptations are most advantageous in avoiding predation. Most species of the Amblysomus genus are solitary animals and therefore do not often pose the risk of predation. Despite this, golden moles must leave their burrow at some point and in these circumstances are at risk of predation via snakes, birds of prey, otters, genets, and jackals. These African animals are widespread and inhabit a range of environments and climates, similar to golden moles which cause a wide range of predators.

The first necessary behavior for predator avoidance is predator reception via seismic vibrations and sounds. In most circumstances, being aware of predators is the only tactic for Amblysomus to avoid predation. Due to the size of golden moles, it is highly unlikely for them to injure an animal larger than themselves. Adaptations for fossoriality correlate with anti-predation adaptations as it is most advantageous for Amblysomus to stay unseen. These adaptations include short, dense, and neutral-toned fur to blend into surrounding environments, and increased vibrational and acoustic sensitivity.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

The fossorial nature of Amblysomus causes disturbances in soil which allows for aeration of their occupied lands. Soil aeration is beneficial for other species for habitats and resources as well as humans for agricultural purposes. Despite their solitary nature, Amblysomus have been seen to share a mutualistic relationship with two species of mole rat, Heterocephalus graber and Cryptomys hottentotus . In doing so, they share the burrow they created together, reducing both energy investments.

Their insectivorous diets allow for a sense of 'pest' control of insects and other invertebrates in urban areas. Amblysomus populations are also controlled by their predators causing the drive of the ecosystem cycle.

• Ecosystem Impact
• soil aeration soil aeration

Economic Importance for Humans: Positive

The only known ecological importance of Amblysomus is the process of soil aeration via burrow creation. Soil aeration relates to the betterment of the soils and lands in areas typically with agricultural purposes.

• Positive Impacts
• controls pest population

Economic Importance for Humans: Negative

Amblysomus do not pose direct harm on humans but may affect agricultural and grasslands. Golden moles are common to encounter humans due to their habitat boundaries which in many cases include golf courses, suburban areas, and agricultural areas. On golf courses, the mounds created by burrowing golden moles are often issues for golfers causing a vulnerability of some Amblysomus species. In agricultural areas, some golden moles may eat the roots as they burrow through crops. The effects of golden moles are indirect.

• Negative Impacts
• crop pest

Conservation Status

Species within the genus Amblysomus have conservation statuses that range between least concern and endangered. The most stable species in Amblysomus hottentotus have a wide habitat range allowing for the least interaction with humans. The most concerning species is Amblysomus marleyi who reside within a 1,500 km mountainous area that is being affected by habitat degradation. The causes of these statuses are mainly due to habitat loss via agriculture and suburban expansion. In many cases, non-seasonal wood harvesting is highly detrimental to members of the Amblysomus genus. Conservation efforts include protected areas of certain species, most importantly Amblysomus hottentotus as they have the widest range. Many species of Amblysomus also reside in National parks that are federally protected such as Amblysomus corriae

Additional Links

Encyclopedia of Life

Contributors

Jordyn Page (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

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