The species is resident in the undergrowth of evergreen forest, including bamboo, often close to streams, from perhaps as low as 350 m up to 2,500 m, but in Bhutan recent records are only between at 1,000-2,100 m (Spierenburg 2005, Dhendup 2015). In Bhutan, its known distribution is almost entirely confined to areas with extensive old-growth forest suggesting that the species may be sensitive to habitat degradation (P. Spierenburg in litt. 2004). Calling birds are heard from mid-March to June (Spierenburg 2005).

Arborophila mandellii is endemic to the eastern Himalayas north of the Brahmaputra, and is known from Bhutan, West Bengal (Darjeeling only), Sikkim and Arunachal Pradesh in north-eastern India, northern Myanmar , south-eastern Tibet, China (MacKinnon and Phillipps 2000, Spierenburg 2005, Zhang et al. 2017, McGowan et al. 2020, Naing et al. 2020, eBird 2021, GBIF 2021). There are recent records spread throughout Bhutan. It is locally common in the remaining forests of Arunachal Pradesh and perhaps also in parts of West Bengal, suggesting it may be evenly distributed right across its range, wherever suitable habitat occurs. While there are records from the low hills (c. 250 m) in the Bhutan duars, most records are from mid-elevations and above 1,000 m, at least in Bhutan (Spierenburg 2005, Dhendup 2015).

A species distribution model has been derived for this species as part of a species-group of galliformes associated with high-density vegetation in the eastern Himalayas (Bagaria et al. 2021). This cohort was predicted to have between 66,044 km² (using bioclimatic envelope models) and 79,852 km² (using the species distribution models) (Bagaria et al. 2021). Within India, the occupied range has been estimated as 13,833 km² (State of India's Birds 2020). From these values, while they have not been calculated at the correct scale to be considered a valid Area of Occupancy (AOO: IUCN 2022), it is very likely that an AOO would considerably exceed the thresholds for listing as threatened under the range size criterion. The Extent of Occurrence (EOO: IUCN 2022), a minimum convex polygon around mapped confirmed and probable occurrence polygons based upon multiple sources (Rasmussen and Anderton 2012, Dunn et al. 2016, Zhang et al. 2017, Naing et al. 2020, eBird 2021, GBIF.org 2021), is estimated at 227,000 km². The species is highly dependent upon forest habitats, and within the mapped range forest cover loss has proceeded at a slow rate, up to 2.4% over the past three generations (data from Global Forest Watch 2021, using Hansen et al. [2013] data and methods disclosed therein). This suggests that there is a continuing decline occurring in the area, extent and also likely in the quality of the species's habitat. 

Bagaria et al. (2021) used their modelled distributions and future climate predictions to predict that this species would be among the Himalayan galliformes most severely impacted by climate change. Under the RCP 4.5 scenario, 47% of currently suitable habitat was predicted to become unsuitable by 2070, while only 8% would become newly suitable (Bagaria et al. 2021). As such, the rate of habitat loss is suspected to accelerate over the next three generations, and is likely to cause a reduction in the EOO and AOO as well as exacerbating the declines in habitat quality.

Conservation Actions Underway
It is known from a number of protected areas: Singhalila National Park, Neora Valley National Park and Buxa Tiger Reserve in West Bengal; Maenam WLS (A. Rahmani in litt. 2012) in Sikkim (but there do not appear to be any recent records here [Acharya and Vijayan 2010]); Namdapha National Park, Mehao, Eaglenest and Dibang Valley Wildlife Sanctuaries in Arunachal Pradesh (Choudhury 2008, A. Rahmani in litt. 2012, eBird 2021, GBIF.org 2021); and Nameri National Park and Subansiri Reserve Forest in Assam (Choudhury 2000, A. Rahmani in litt. 2012). It is found in several protected areas in Bhutan, including Jigme Singye Wangchuck National Park, Thrumshing La National Park, Jigme Dorji National Park and Jomotsangkha Wildlife Sanctuary (Inskipp et al. 2000, BirdLife International 2001, eBird 2021, GBIF.org 2021).

A recent ban has been placed on timber export from forests in Arunachal Pradesh. Bhutan's national policy to maintain forests over 60% of the country potentially goes a long way to ensuring a safe long-term future for this species there, and c. 35% of the country is designated as a Protected Area (26%) or Biological Corridor (9%) (P. Spierenburg in litt. 2004).

Conservation Actions Proposed
Conduct intensive studies at key sites to provide detailed information on population densities and threats. Assess the threat posed by trapping and hunting pressure (A. Rahmani in litt. 2012). Conduct awareness programmes to reduce trapping and hunting pressure (A. Rahmani in litt. 2012). Conduct long-term studies at key sites to provide detailed information on habitat use and to monitor range shifts in the species. Establish a network of monitoring sites to ground-truth remote sensed data in order to track the rate and type of changes occurring due to climate change, and test the predicted rate of loss of habitat for the species (after Bagaria et al. 2021).