[5] They resemble the smaller 'northern cave' species Vespadelus caurinus, except for the darker colouring lacks a yellowish hue.

[10][11] The specific epithet "douglasi" honours the work of Marion and Athol M. Douglas, for their contributions to research of Australian bats.

Anthropogenic threats to the population include disturbance while roosting by visitors to caves and loss of habitat due to agricultural practices.

[10] The areas in which they forage are streams running through tropical woodland, riparian zones dominated by pandanus and melaleuca trees within the 800 mm isohyet.

[2][11] They maintain small groups, typically foraging in tropical woodland vegetation and often observed hunting over open running water.

[2] The breeding behavior is largely unrecorded, it is assumed that copulation takes place in the wet season due to an observation of lactation at a maternity colony in March.

These are tiny disc shaped organisms that reside at the ears or wings, under the stratum corneum, as a low grade infestation.