Taxonomic Notes
The status of Varanus ocellatus is uncertain; it has been variously treated as a synonym of either V. albigularis or V. exanthematicus (Bennett 2004). This account follows Bennett (2004) in considering this form a synonym of V. exanthematicus with a distribution in Sudan (presumably South Sudan given the distribution for V. exanthematicus provided by this author). Specimens from Djibouti, Somalia and Ethiopia previously attributed to V. ocellatus are now understood to represent V. albigularis (Ineich 2001, Largen and Spawls 2006).
Justification
Assessed as Least Concern. Although current exploitation levels are considered sustainable, the scale of exploitation for this species in Nigeria and countries further east is unknown and may be significant. Further research and monitoring is recommended to ensure that levels of exploitation do not increase leading to widespread declines; specifically to assess population trends of the heavily harvested populations in Ghana, Togo and Benin, and to evaluate the management of their established ranching system.
Geographic Range Information
This widespread monitor lizard is found in sub-Saharan Africa north of the equator (Bennett 2004). It is known to occur from Senegal, from where it was first described, eastwards to Eritrea (records from Ethiopia previously attributed to the synonym Varanus ocellatus are now understood to represent V. albigularis - Largen and Spawls 2006). Its southern range limit within this region is unclear, particularly in areas where its range may coincide with that of the White-throated Monitor (Varanus albigularis) (Bennet 2004). It is listed by Bennett (2004) as occurring in Liberia and Sierra Leone, however, Trape et al. (2012) do not include records of its occurrence in these countries. The species has also been recorded in Guinea Bissua (mainland and the Bijágos Islands) (Auliya et al. 2012). Its occurrence in Sudan and Kenya requires confirmation due to the occurrence of the similar V. albigularis in these regions, and its occurrence has only recently been confirmed in Murchison Falls and Moyo in northeastern Uganda (Spawls et al. 2018). It is mapped for South Sudan by Bennett (2004), an area not included in the distribution of V. albigularis provided by Bayless (2002) but included in that described by Spawls et al. (2018). It is unlikely to be common at elevations above 800 m above sea level (D. Bennett pers. comm. 2010), although it has been recorded up to 1,400 m asl (Spawls et al. 2018). One animal was recently collected from an urban area in Puerto Vallarta in Mexico (Cupul-Magana 2010), suggesting that an introduced population may be established in this country.
Population Information
This species is common in some habitats, particularly in sparsely inhabited areas and those that are protected. Within and around low-intensity agricultural areas, population densities can be quite high (Bennett and Thakoordyal 2003). In Ghana it is most common on sandy soils, particularly in areas with mosaics of agricultural and uncultivated land (Bennett 2004). Juvenile densities can be as high as 357 per square kilometre, indicating a density of around 24 adult females per km2 (Bennett 2000). Average encounter rates of 0.43 ± 0.28 adults and 0.54 ± 0.47 juveniles per hour have been recorded in good habitat (Bennett 2004). There is no information on population trends, with historical accounts from different parts of the lizard's range indicating that it was rare (in what are now the Democratic Republic of the Congo and South Sudan) or common (in Guinea-Bissau and Nigeria) (Bennett 2004 and references therein).
Habitat and Ecology Information
The western Savanna Monitor is restricted to grasslands and agricultural areas within the savanna belt (D. Bennett pers. comm. 2010). Bennett (2004) observes that the species occurs in woodlands within the savanna belt, but that it is absent from rainforest, although there are reports from riverine forest near the Togolese border (Bennett 2004). It can occur in reasonably dry areas, and unlike the sympatric Nile Monitor (Varanus niloticus) is not confined to regions close to water sources. It is, however, strictly active during the wet season, aestivating in tree holes or in burrows in the dry season (Trape et al. 2012), the latter in more sparsely-wooded areas (Bennett 2004). Animals may use burrows dug by other species; in farmland in the coastal plains of Ghana, juveniles appear largely reliant on burrows dug by the cricket Brachytrupes membranaceus (which also serves as their most important prey species in these areas until they outgrow the crickets' burrows - Bennett 2004). Animals also make use of abandoned termite mounds or mammal burrows (Bennett 2004). Prey includes insects, scorpions, myriapods, and gastropods (Trape et al. 2012), although the latter seem uncommon food items despite the lizard's apparent morphological adaptations for penetrating snail shells (Bennett 2004). It will sometimes feed on the eggs of lizards and frogs (Trape et al. 2012), but preys almost exclusively on arthropods (Bennett 2004). Females have a maximum clutch size of 41 eggs; near Accra the average clutch size appears to be 18 (Bennett 2004 and references therein). Usually clutch size comprises between 6 and 29 eggs (Auliya and Koch 2020). Up to four clutches may be produced a year (Bennett 2004), but this number is in need of confirmation.
Threats Information
The Savanna Monitor is hunted for food in some West African countries and is used in traditional medicine. It is the most common varanid in the pet trade and more than 100,000 wild individuals are exported every year (Bennett 2001); it is also heavily exploited for its skin. Based on extensive field studies, Bennett and Thakoordyal (2003) conclude that even the present high level of collection for export is sustainable. It may be the case that in certain areas populations may be declining, but there are not thought to be any major threats to this species.
Use and Trade Information
This species is hunted for food in some West African countries and is used in traditional medicine (see Segniagbeto et al. 2013). It is also heavily exploited in both the skin and pet trade (cf. de Buffrénil 1995, Harwood 2003, Ineich 2006). It is the most common varanid in the pet trade and more than 100,000 wild individuals are exported every year (Bennett 2001). From 1975-1986, 13,000 live exports and 1,370,000 skins exports were reported (King and Green 1999). The CITES database recorded just short of 650,000 individuals traded in the period from 1975–2005 (Pernetta 2009). Between 2010–2017, the three major West African exporting countries, i.e. Ghana, Togo and Benin exported 211,050 live specimens destined for the international pet trade (CITES trade database). Between 2015–18, all three countries exported 53,940 live specimens, of which 48% were sourced from ranching operations. This species breeds very rarely in captivity. A large number of gravid females are taken from the wild every year for ranching purposes, but survival rates of females after egg-laying are likely to be very low so that the system requires annual collections of wild females for restocking (D. Bennett pers. comm. 2010).
Conservation Actions Information
This species is listed in CITES Appendix II. It is likely that areas of this species' distribution coincide with protected areas. Further research into the harvest levels of this species is recommended, as although previous studies have been conducted and found no evidence of an impact from trade the species might be at local risk in some areas. The expansion and management of protected areas within this species range could provide a refuge for this species from hunting.