Tag Archives: Mexican Free-tail Bat

Habitat of Ruby

Ruby has worked with the Arizona Game and Fish Department and the U.S. Fish and Wildlife Service to better understand and protect the area’s wildlife. A big-game fence was constructed around the perimeter to allow access for wildlife and help protect the property’s ecosystem.  This fence allowed ash and many other trees to mature in an area that was overgrazed by cattle.  It is now a forest with a drainage system continuing down the valley.

Several film companies have  documented the biodiversity of Ruby, and one group, Oxford Scientific Films from the U.K., produced a video, “The Ghosts Of Ruby” which airs regularly on PBS and Discovery channels. Others use it for filming drama and photogenic properties & music videos.

Surveys and documentation of the wide variety of plants and animals of the area  for the next several years will be done by  biologists from several agencies and conservation groups to understand in greater detail Ruby’s potential as a wildlife refuge.  There are many independent experts with love for the land, its history and the value to human as is!

A colony of Mexican Free Tail Bats inhabits Ruby’s abandoned mine shafts from May to September each year. Estimates of the colony range from 90,000 to as high as 150,000 animals , representing a nightly appetite for up to 1/2 ton of insects.  This is considered a maternal colony and they produce the young in June and leave for parts south in late August.  Their nocturnal schedule varies with storm, wind and insect life.

Ruby is very interested in furthering the educational benefits of outdoor classrooms in “the wild”.  There are a couple ongoing proposals 2021.  More later!

Montana Mine Bat Habitat

The largest number of bats appears to be the Mexican Free-Tailed Bat (Tadarida brasiliensis)…family:  Molossidae.


Montana Mine underground shaft is one of the most species diverse roosts in southern Arizona.
~Brian Corbett, BCI





These medium-sized bats have a wingspan about 12 inches and weigh 10-12 grams.  They have short grayish fur with long and slender wings, round ears and wrinkled upper lips.  These bats are migratory, spending summers in N. Mexico and the US and wintering in Mexico and very south US.  They breed in late February and early March.  One or two young/female are born in mid-June to early July.  Young develop rapidly and begin flying in 4-5 weeks.  When emerging at sunset they are predated upon by raptors, owl and snakes. (they sometimes fall to the ground at Ruby).Photography by David Bygott

The Mexican free-tail bats emerge from a roost around sunset to forage and drink.  They are fast and efficient fliers and usually hunt within a 50 mi. radius, but could forage up to 150 miles.  These feed primarily on moths but numerous other insects as well.  Nursing females require large quantities of insects that are high in fat, such as egg-laden moths.  The Mexican free-tail bats are adept aerial hunters who eat their prey in flight and often forage in groups.Photography by David Bygott

Mexican free-tail bats roost in tight clusters in caves, mines, tunnels, crevices in bridges, buildings, attics and hollow trees.  Many roosts are used in spring and fall during migration.  At Ruby we have the bats mainly April until late August.  Their arrival and departure varies with drought and insect availability seemingly.  Ruby probably has a maternal colony.  Most of the very large maternity colonies are in Texas and Mexico although the Ruby colony has been estimated by biologists at 70,000 to 200,000.  It fluctuates year to year.

Threats to Mexican free-tailed bats include pesticides and destruction or disturbance to roost sites.  Suitable sites for large maternity colonies are extremely limited.

Bats found in the underground shafts of Montana Mine:

  1. Tadarida brasiliensis – Mexican free-tailed bat
  2. Eptesicus fuscus – Big brown bat
  3. Corynorhinus townsendii – Townsend’s bit-eared bat
  4. Choeronycteris Mexicana – Mexican long-tongue bat
  5. Myotis thysanodes – Fringed myotis
  6. Myotis velifer – Cave myotis
  7. Myotis californicus – California myotis
  8. Myotis ciliolabrum – Small-footed myotis