The species occurs in grasslands, open woodlands and second-growth forest (Hoogstraal 1951). It has a gestation length of approximately 180 days, with typically one young, and rarely twins. Age at sexual maturity is 8-12 months, with a life span of 12-20 years. This species is diurnal, browses on leaves, and lives in small herds (Wemmer 1998). This species has a group size up to 27 individuals, but usually 7–14 (with much smaller groups reported in heavily hunted areas; Oliver and Villamor1992).

This species is endemic to the Philippines, where it is restricted to the Calamian Islands in the Palawan faunal region. The species occurs on three of the four larger islands in Calamians, i.e. Busuanga, Calauit and Culion, but is absent from Coron (Oliver 1993, Oliver and Villamor 1993, Heaney et al. 1998, Grubb 2005). The species is also reported to have occurred on at least nine other smaller islands, including three islands where small numbers of individuals translocated from Calauit were released in the late 1980s (Oliver and Villamor 1993). However, it was reported to be extinct on at least seven (78%) of these islands (Bacbac, Capari, Panlaitan, Galoc, Apo, Alava and Dicabaito), and to survive on only two of these islands, namely Marily and Dimaquiat (Rico and Oliver 2008). It is not known from anywhere else in the region, including mainland Palawan, nor the larger and intervening of island of Linacapan.

Calamian Deer occurs in the Calauit Island Game Preserve and Wildlife Sanctuary (37.4 km²), which was established in 1976 to protect a collection of free-ranging African ungulates (see under Threats). Protection is inadequate and there are no management plans (Oliver 1993). Several hundred local people were evicted at that time it was established, but many of these have since returned to settle illegally (Oliver and Villamor 1993). Thirty animals were introduced to Calauit in 1977 to supplement a small relict population (Orig and Rosell 1994).

The following conservation actions are recommended:

1. Monitor current status on all the three islands and determine population trends. Evaluate levels of hunting and habitat loss.
2. Strengthen existing protected area system via establishment of new (additional) reserves and development and implementation of properly structured conservation management plan for Calauit that includes improved infrastructure, and measures to combat poaching.
3. Agree and establish a zoning system within Calauit in collaboration with all relevant stakeholders, which enforces strict protection of the core area.
4. Establish protected areas on Culion and Busuanga, based on habitat and deer status surveys.
5. Undertake behavioural and ecological research of Calauit Deer to determine management requirements. Conduct more detailed studies in selected areas.
6. Initiate a conservation education program using Calamian Deer as a flagship species to promote a wide variety of related conservation activities, including combating the bushmeat trade.
7. The species is now thought to have gone extinct on the main island of Palawan relatively recently (Piper et al. 2008). It is suspected that loss of habitat due to sea level rise and transformation of grass- and open woodlands into closed forests are the main reasons for the extinction of the species on Palawan. Due to human activities many of these semi-open habitats now exist again in the former range on Palawan. Reintroduction to the main island of Palawan may therefore be one tool to reduce the extinction risk of the very localized and declining populations in the Calamian group of islands.
   

This species is listed on CITES Appendix I.