There are no major threats to Onthophagus cyaneoniger as it has been recorded abundantly on various dung types, including cattle dung. Furthermore, it has been found in both farm grassland and fallow crop fields grazed by domestic livestock with protection also afforded by its occurrence in nature reserves. Therefore, it is classed as Least Concern.

This species is centred on the drier western parts of the cool south-east highlands of South Africa, with peripheral records in the Northern Cape, Upper Karoo and coastal Eastern Cape (Davis et al. 2020). It was described from an unspecified locality in the Transvaal (now divided into four provinces, Gauteng, Northwest, Mpumalanga and Limpopo). Records from Botswana, the Democratic Republic of Congo, and Zimbabwe (Schoolmeesters 2011) lie outside the known range and require validation (Davis et al. 2020). The patchy records across its known range may be a collecting artifact resulting from its very small body size, but may potentially reflect soil specialisation (Davis et al. 2020).

This species can be locally abundant in parts of its range.

Collection records are primarily from sandy loam on cattle dung in grassland, with one record from a ploughed field (Australian CSIRO 1970-1986, unpublished records). Smaller numbers have been recorded from sand and sandy clay loam (Davis et al. 2020). In a survey at the northern edge of its range in Gauteng Province, South Africa (latitude 25-26 °S), this very small-bodied species was trapped with composite baits of pig and cattle dung in nature reserves. This study found it to occur on sand or finer-grained sandy loam soils, where it was abundant between the altitudes of 1,350-1,550 m (22.4 individuals per trap in Ezemvelo, 68.1 per trap in Abe Bailey) (Davis et al. 2005). It was rare in a reserve situated above (1,650-1,900 m) (0.2 per trap in Suikerbosrand) and absent from three reserves situated below this altitude (1,100-1,300 m) (Davis et al. 2005). On three farms situated within the upland edge of the Nama Karoo at the margin of Highveld grassland outliers, this species was trapped with composite baits of cattle dung and sheep pellets. It occurred in abundance on one farm (29.4 individuals per trap on Gordonsfontein), becoming uncommon with increasing distance from the Highveld grassland (1.8 per trap on Oppermansdam, 0.04 per trap on Raapfontein) (Scarab Research Group, University of Pretoria, unpublished data)

This species is centred on the drier Highveld grassland (AT1009), with a few records from adjacent ecoregions, particularly the higher altitude southeast of the Kalahari xeric savanna (AT1309) and high elevation localities at the very edge of the Nama Karoo (AT1314) in the Eastern Cape (ecoregions based on Olson et al. 2001). There are also single outlier records from pasture in the Knysna-Amatole montane forests (AT0115) and the Drakensberg montane grasslands, woodlands and forests (AT1004).

Some environmental characteristics for 42 locality records are as follows: mean elevation 1,394 ± 297 (S.D.), range: 290-1,860 m; mean annual rainfall 308-1,022 mm; mean annual temperature 13.2–19.5 °C (Davis et al. 2020).

This species is unlikely to be under serious threat as it occurs in abundance on some farms as well as in nature reserves. As it has also been recorded from a ploughed field where cattle are often allowed to graze on stubble of cereal crops after harvest, it may be less threatened than other species by the high rate of land transformation in drier Highveld grasslands (up to 67% of the original vegetation in these vegetation units having been lost) (Low and Rebelo 1998).

There is no use or trade information available for this species.

No species-specific conservation measures in place, or needed, at present, particularly as the species is provided with a measure of protection in some nature reserves, including Telperion, Suikerbosrand, Ezemvelo and Abe Bailey in Gauteng Province, South Africa (Davis et al. 2005). Although it is not presently considered to be at significant risk it occurs in a highly transformed area, so research is recommended to clarify whether it is impacted by pasture improvement or other forms of habitat modification (Davis et al. 2020).