Bulbophyllum oxycalyx is endemic to Madagascar and is known from 28 collections and two observations (18 occurrences). Three of these collections (Bosser 17070, Herb. Jard. Bot. Tana 1306 and Herb. Jard. Bot. Tana 430) were made with no precise locality information and thus were not taken into account in this evaluation. Twelve collections and two observations representing eight occurrences were made in seven protected areas, Marojejy National Park (one occurrence, one location), Tsaratanana Natural Reserve (one occurrence, one location), Loky-Manambato National Park (two occurrence, one location), the Torotorofotsy Protected Area (one occurrence, one location), Ambohitantely National Park (one occurrence, one location), Ivohibe Special Reserve (one occurrence, one location) and Mantadia National Park (one occurrence, one location). In addition to these legally protected sites, nine collections representing three occurrences were made within the footprint of a mining project and have been subjected to intense human pressure from forest clearing and should now be considered as extirpated. One collection (one occurrence) has been made in the Conservation Zone surrounding the mine footprint at a site undergoing intense human pressure due to forests clearing. This zone should be protection in the near future. Bulbophyllum oxycalyx is also known from three collections made from Ankazobe, Angavokely and around Maevatanana (three occurrences) made in unprotected forests subjected to selectve wood harvest, charcoal production, timber harvesting for small-scale subsistence use, and slash-and-burn agricultural practices (tavy). The species is thus known from 25 collections and two observations with precise locality information, representing 12 existing and three extirpated occurrences.

The extent of occurrence (EOO) of Bulbophyllum oxycalyx is estimated to be 112,165 km² (exceeding the upper limit for vulnerable status under criterion B1) whereas its area of occupancy (AOO) is estimated at 48 km² (within the limits for Endangered status under the criterion B2). These 12 existing occurrences represent a total of 11 locations (sensu IUCN 2019) with respect to the most plausible serious threat, forest clearing due to mining activities, only just exceeding the upper limit for Vulnerable status under criterion B. It is inferred that ongoing loss of its habitat will induce a continuing decline in EOO, AOO, habitat extent and quality, and the number of subpopulations and mature individuals. Bulbophyllum oxycalyx is therefore assigned a status of Near Threatened as it almost qualifies for listing as threatened under criterion B2.

Bulbophyllum oxycalyx is endemic to Madagascar where it is known from the former provinces of Antananarivo in the Analamanga Region (Angavokely, Ankazobe and Ambohitantely), of Antsiranana in the Diana and Sava Regions (Daraina, Marojejy and Tsaratanana), of Toamasina in the Alaotra-Mangoro Region (Moramanga and Mantadia) and Fianarantsoa in the Ihorombe Region (Ivohibe).

The population of Bulbophyllum oxycalyx is currently thought to be decreasing since its habitat is threatened by forest clearing due to mining activities, and forest degradation due to forest exploitation and timber harvesting for small-scale subsistence and slash-and-burn agricultural practices (tavy). The number of mature individuals of B. oxycalyx is not known and cannot be estimated since the species is an epiphyte on the trunk or branches of trees in the canopy.

Bulbophyllum oxycalyx is an epiphyte herb growing on the trunk or branches of trees in the canopy in humid and subhumid forests at altitudes between 1,014 and 1,700 m. (Madagascar Catalogue 2020). It does not grow in direct sunshine and grows near the ground in the understorey of the forest.

The species experiences continuing decline in EOO, AOO, habitat quality, and the number of locations and mature individuals because of habitat destruction due to mining activities, forest exploitation to timber harvesting for small-scale subsistence and slash-and-burn agricultural practices (Tavy).

There are no reported uses for this species, but it may be sought after by specialist collectors.

Bulbophyllum oxycalyx has been recorded from seven protected, Marojejy National Park, Tsaratanana Natural Reserve, Loky-Manambato National Park, the Torotorofotsy Protected Area, Ambohitantely National Park, Ivohibe Special Reserve, and Mantadia National Park. One collection (one occurrence) of this species has also been made in the conservation zone surrounding the footprint of a mining project. This zone should be protection in the near future. The species is listed in CITES Appendix II. It has been brought to cultivation at the Ambatovy shade houses. Ex situ conservation is recommended (micro-propagation, seed banking). Further awareness building is recommended for local communities and national authorities.