Overview

Dendromus mesomelas s.l. – (Brants, 1827) 

ANIMALIA – CHORDATA – MAMMALIA – RODENTIA – NESOMYIDAE – Dendromus – mesomelas 

Common Names: Brant’s Climbing Mouse, Chestnut Tree Mouse (English), Brants se Klimmuis, Rooiboommuis (Afrikaans)   

Synonyms: Mus mesomelas (Brants, 1827); Dendromus typus A. Smith, 1829; Dendromys (?) typus Wagler, 1830; Dendromys mesomelas Smuts, 1832; Dendromys typicus A. Smith, 1834; Dendromys pumilio J. A. Wagner, 1841; Dendromys mesomelas pumilio Fitzinger, 1867; Dendromus mesomelas Thomas & Schwann, 1906; Dendromus pumilio Wroughton, 1907; Dendromus ayresi A. Roberts, 1913; Dendromus mesomelas major St. Leger, 1930; Dendromus mesomelas pumilio Shortridge, 1942 

Taxonomic Note:  
Represents a species complex as a recent phylogenetic study by Voelker et al. (2021), identified eight distinct evolutionary lineages with distributions ranging from South Africa to Tanzania and Uganda. The species type locality is reported as “east of Port Elizabeth, Sunday’s River, Eastern Cape Province, South Africa,” however at least three separate genetic lineages have been described from South African samples alone (Voelker et al. 2021). As such, the taxon is referenced as D. mesomelas s.l., pending further taxonomic investigations. Although previously included within this species, D. insignis, D. oreas and D. vernayi are now considered valid species (Monadjem 2013; Monadjem et al. 2015). Chromosomal analysis by Solano et al. (2014) reveals further potential species splits; for example, populations in Mozambique, Zambia and Botswana that are isolated from those in South Africa may in fact reveal separate species. A comprehensive integrative taxonomic approach is urgently needed to resolve the present uncertainties regarding the evolutionary origins of southern African taxa within the genus Dendromus.  

Red List Status: LC – Least Concern

Assessment Information

Assessors:  Richards, L.R.¹, Naidoo T.¹ & da Silva, J.M.² 

Reviewers: Patel, T ³. 

Institutions:¹Durban Natural Science Museum,²South African National Biodiversity Institute,³Endangered Wildlife Trust 

Previous Assessors and Reviewers: MacFadyen, D., Shoeman, C. & Relton, C. 

Previous Contributors: Child, M.F., Avenant, N., Avery, M., Baxter, R., Monadjem, A., Palmer, G., Taylor, P. & Wilson, B. 

Assessment Rationale 

Listed as Least Concern, as this species is widespread along the eastern grassland regions of the assessment regions, occurs in many protected areas, and is fairly common. However, although there is no evidence for large-scale population decline at present, continued loss of grassland habitat would certainly impact it in the future. Although its fynbos habitat is well-protected in the south of its range, grassland habitats in the north are severely threatened and fragmented. This species needs high-quality grassland to survive. Loss of area of occupancy through grassland loss should be systematically monitored and this species should be reassessed when finer-scale data emerge. Taxonomic resolution, by assessing which populations / genetic clades qualify for being upgraded to species level, is required and may necessitate reassessment in future.

Regional population effects: Populations are isolated within countries, and rescue effect is unlikely because there is a disjunct distribution between the assessment region and rest of the species range. 

Reasons for Change 

Reason(s) for Change in Red List Category from the Previous Assessment: No change 

Red List Index 

Red List Index: No change 

Recommended Citation: Richards LR, Naidoo T & da Silva JM. 2025. A conservation assessment of Dendromus mesomelas s.l.. In Patel T, Smith C, Roxburgh L, da Silva JM & Raimondo D, editors. The Red List of Mammals of South Africa, Eswatini and Lesotho. South African National Biodiversity Institute and Endangered Wildlife Trust, South Africa.

Regional Distribution and occurrence

Geographic Range 

While previously considered to occur widely across African highlands, recent molecular evidence suggests D. mesomelas is restricted to south of the Zambezi River while north occur several taxa now listed as valid species including D. insignis, D. nyasae, D. oreas and D. vernayi (Monadjem 2013, Monadjem et al. 2015). Within the assessment region, it occurs widely in the eastern and southwestern grassland regions of the country, including Eswatini and Lesotho along an altitudinal gradient, from sea level, in the southern portions of its range, to montane areas in the north (Skinner and Chimimba 2005, Monadjem 2013, Monadjem et al. 2015). The distribution is reported to marginally intrude into the North West Province (Skinner and Chimimba 2005), but was not detected during a 2014 survey (Power 2014). Further vetting of historical museum records is required to confirm this extension of their range. 

Elevation / Depth / Depth Zones 

Elevation Lower Limit (in metres above sea level): 0 m asl  

Elevation Upper Limit (in metres above sea level): recorded at 2,400 m asl (Rowe-Rowe and Meester 1982) 

Depth Lower Limit (in metres below sea level): N/A 

Depth Upper Limit (in metres below sea level): N/A 

Depth Zone: N/A 

Map 

Figure 1. Distribution records for Brant’s Climbing Mouse (Dendromus mesomelas) within the assessment region (South Africa, Eswatini and Lesotho). Note that distribution data is obtained from multiple sources and records have not all been individually verified.

Biogeographic Realms 

Biogeographic Realm: Afrotropical 

Occurrence 

Countries of Occurrence 

Large Marine Ecosystems (LME) Occurrence 

Large Marine Ecosystems: N/A 

FAO Area Occurrence 

FAO Marine Areas: (Not specified) 

Climate change

To date, no formal studies have examined the potential impacts of climate change, along with associated bioclimatic and environmental shifts, on the biology, ecology, or physiology of this species. The species is more commonly associated with grass-dominated landscapes and appears to be stricter in its habitat preference than other Dendromus species, exhibiting a strong affinity for moist habitats (Monadjem 2013; Monadjem et al. 2015). Midgeley and Thuiller (2010) predicted a 30% replacement of grassland-dominated habitats by more arid-adapted or tolerant vegetation types (e.g. thorn-scrub savanna). This may result in the displacement or range contraction of grassland-associated species, that may include Dendromus mesomelas s.l. within the assessment region. Rodent population declines tend to be more pronounced in habitats experiencing significant anthropogenic transformation or, alternatively, in high-altitude environments where the effects of climate change are likely to be intensified (Wan et al. 2022). Further research is required to assess the potential impacts of climate change on this species within the assessment region. 

Population Information

Within temperate grasslands and moist montane habitats of the assessment region, this species occurs commonly. For example, they are relatively numerous in the leaf-litter of afromontane forest in Eswatini (Monadjem 2013). No density estimates are available. Subpopulations are separated by regions of unsuitable habitat and fluctuations occur seasonally. 

Population Information 

Current population trend: Stable   

Continuing decline in mature individuals?  Unknown, but unlikely.  

Extreme fluctuations in the number of subpopulations: Cannot be determined as there is a general lack of information on population ecology. 

Continuing decline in number of subpopulations: Unknown 

All individuals in one subpopulation:  Unknown, pending phylogenetic and phylogeographic studies 

Number of mature individuals in largest subpopulation: Unknown 

Number of Subpopulations:  Unknown, pending phylogenetic and phylogeographic studies 

Quantitative Analysis 

Probability of extinction in the wild within 3 generations or 10 years, whichever is longer, maximum 100 years: Unknown, but unlikely.  

Probability of extinction in the wild within 5 generations or 20 years, whichever is longer, maximum 100 years: (Not specified) 

Probability of extinction in the wild within 100 years: (Not specified)

Population Genetics

Recent phylogenetic investigation of the genus Dendromus revealed cryptic diversity within D. mesomelas, with eight lineages currently included under this taxon (Voelker et al. 2021). The specific geographic distributional limits and ecological niches of these lineages remain unresolved and requires further investigation. Within the assessment region, several subpopulations may exist; however; it is unclear as to whether these form a single metapopulation or separate genetically distinct groups potentially due to habitat fragmentation and limited dispersal capabilities. A comprehensive population genetic study is recommended to elucidate the genetic structure and diversity within this species.  

Habitats and ecology

Similar to other Dendromus species, Brants’ Climbing Mouse is associated with grassland or marsh vegetation, especially in tall grasses with shrub (Taylor 1998, Monadjem 2013). In the southern portions of its range, they have been recorded within forest – grassland mosaic and fynbos habitats. It has also been sampled in Palmveld (Hyphaene coriacea) in KwaZulu-Natal (Rautenbach et al. 2014), swamps and Afromontane forests (Rowe-Rowe and Meester 1982, Monadjem 1998). However, they appear to be more restricted to high quality grassland habitats further north. During recent surveys in Gauteng and Mpumalanga, this species was not recorded in the Rocky Highveld Grassland of Ezemvelo Nature Reserve (Gauteng) and Telperion (Mpumalanga) (MacFadyen 2014). This species prefers tall, rank grassland with a high plant biomass, but is also recorded in areas with low woody vegetation. The species has a reported preference for moist habitats, being notably absent from arid and semi-arid environments (Monadjem 2013). It appears more specific in its habitat requirement when compared with D. melanotis and D. mystacalis. As such, it does not occur in modified landscapes and thus loss of natural grasslands impacts severely on the species. 

This omnivorous species feeds on seeds, as well as a wide range of invertebrates, which contribute to their diets at varying proportions depending on their local conditions. For example, in the Okavango Delta, where they have no access to seeds, they were found to feed exclusively on insects (Smithers 1971), however, in other regions, invertebrate consumption is likely correlated with seasonal changes in abundance (Monadjem 2013). In the Drakensberg and Eswatini, their diets comprised mostly of grass seeds (Rowe-Rowe 1986, Monadjem 1997). Like other species of climbing mice, this nocturnal and largely terrestrial species accesses seeds and invertebrates in low bushes and grass stalks, using its prehensile tail to steady itself. The species is usually solitary, in pairs or small family groups. 

Similar to other southern African Dendromus species, these rodents construct round grass nests with entrances at both ends (Roberts, 1954). Nests may be positioned either above or below ground (Kingdon 1974). They are also known to utilize abandoned weaver and warbler nests as sites for raising their young or for resting (Roberts, 1954; De Graaff, 1981). The species is largely nocturnal but is known to be active during and may share the runways of Otomys in high altitudinal grasslands (Kingdon 1974). 

Ecosystem and cultural services: There are no cultural services or folklores associated with this species. However, similar to other small mammals, this species plays a role in regulating invertebrate numbers, seed predation, nutrient cycling, and is an important prey species for predators. 

IUCN Habitats Classification Scheme 

Life History 

Generation Length: Unknown 

Age at maturity: female or unspecified: Unknown 

Age at Maturity: Male: Unknown 

Size at Maturity (in cms): Female: Mean head and body length= 7.40 cm (De Graaf 1981) 

Size at Maturity (in cms): Male:  Mean head and body length= 7.60 cm (De Graaf 1981) 

Longevity: Unknown 

Average Reproductive Age: Unknown 

Maximum Size (in cms): Female maximum head and body length = 8.5 cm; male maximum head and body length = 8.0 cm (De Graaf 1981) 

Size at Birth (in cms): Unknown 

Gestation Time: Unknown 

Reproductive Periodicity: Animals in breeding condition have been recorded in November (Rowe-Rowe and Meester 1982). Likewise, pregnant females have been collected during the same month (Taylor 1998). 

Average Annual Fecundity or Litter Size: 2-6 pups per litter (Hanny 1965, Taylor 1998).  

Natural Mortality: Dendromus spp. skeletal remains recovered from Barn Owl (Tyto alba; Vernon 1972; Durban Natural Science Museum specimen records), Grass Owl (Tyto capensis; Davis 1973), and Black-winged Kite (Elanus caeruleus; Mendelsohn 1982) regurgitated pellets. Also eaten by a variety of meso-carnivores, including Black-backed jackal (Lupelella mesomelas; Rowe-Rowe 1983). 

Does the species lay eggs? No 

Does the species give birth to live young: Yes 

Does the species exhibit parthenogenesis: N/A 

Does the species have a free-living larval stage? N/A 

Does the species require water for breeding? N/A 

Movement Patterns 

Movement Patterns: Movement and dispersal patterns remain poorly understood / unreported.  

Congregatory: The species typically occurs alone, in pairs, or in small family groups. These family groups may continue to use the grass nest even after the young have been weaned (Skinner & Chimimba, 2005). 

Systems 

System: Terrestrial 

General Use and Trade Information

There is no known subsistence or commercial use of this species. 

Local Livelihood: None reported or known at present.  

National Commercial Value: None reported or known at present. 

International Commercial Value: None reported or known at present. 

End Use: None reported or known at present. 

Is there harvest from captive/cultivated sources of this species? None reported or known at present. 

Harvest Trend Comments: None reported or known at present. 

Threats

Although not believed to be currently declining, threats to this species are grassland habitat loss from agricultural expansion, forestry and mining developments. Loss of habitat quality from overgrazing and incorrect fire management may also cause local declines. Climate change is also expected to reduce afromontane grassland (Taylor et al. 2024), further jeopardising the species similar to other afromontane species (Taylor et al. 2016). The indiscriminate use of chemicals in agricultural industry and urbanisation is also expected to have an impact on this species. The impact of these threats on the population remains to be quantified. 

Conservation

This species occurs in several protected areas within its range in the assessment region including the Cedarberg Wilderness Area, Tsitsikamma National Park, uKhahlamba Drakensberg Park, and iSimangaliso Wetland Park. Protected area expansion to incorporate grassland habitats is a key intervention for the species, specifically to create habitat linkages where connectivity between natural habitat patches has been lost. Planners should prioritise previously cultivated areas for development instead of remaining natural areas. For example, previously ploughed areas now left fallow make up 8.9% of the grassland biome in Mpumalanga, and these areas should be prioritised for further development (Lötter et al. 2014). Grassland restoration projects are also likely to benefit this species. Landowners are responsible for managing the land and vegetation, ensuring that under- or overutilisation of grasses is avoided. This species would also benefit from correct fire and land management practices that conserve grassland habitats. 

Recommendations for land managers and practitioners: 

• Landowners should promote and maintain corridors of grassland between cultivated areas. 

• Employ correct land management practices to prevent overgrazing and indiscriminate burning. 

• Protected areas expansion through provincial biodiversity stewardship programmes. 

• Reduce over-stocking on cattle and game ranches. 

Research priorities: 

• This is a species complex that requires taxonomic revision. The species might be split along biome boundaries. 

• Conduct phylogeographic and landscape genetic analyses to elucidate the genetic structure of animal populations within the assessment region.  

• Land cover maps and climate-based modelling must be used to project future decline in the Grassland Biome and potential impact on the distributional range of the taxon within the assessment. 

• Quantifying habitat preferences and understanding local movements and dispersal mechanisms between habitats; quantifying the species’ habitat under formal protection. 

• Research into the reproductive biology and physiology of the species and the potential impacts of climate change associated extreme fluctuations in temperature and precipitation seasonality on the species.  

• Research into the contribution of this species complex to ecosystem functioning. 

Encouraged citizen actions: 

• Report sightings on virtual museum platforms (e.g., iNaturalist and MammalMAP), especially outside protected areas. 

• Deceased specimens should be submitted to the nearest accredited museum or biological repository for proper documentation and preservation.   

• Plant indigenous species in gardens. 

• Create corridors to offset the impacts of urbanisation and ensure movement and gene flow between populations. 

• Reduce use of insecticides and herbicides. 

• Proclaim private land nature reserves/protected areas under government stewardship program. 

Bibliography

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