bats, and no sign of bat use was found The largest quantity of bat guano was found under the 

 downstream end of the bridge near Norris Campground No sign was found on or under the 

 wooden road structure at Beryl Springs, a thermal area that passes under the road span 



Undeveloped thermal areas The Geyser Springs Group of the Norris Geyser Basin is a 

 known maternity site for an undetermined species of Myotis (S Martinez personal 

 communication) This site was visited to search for roosting bats or signs of use under the 

 boulders in the thermal area (where the roost is located) Numerous boulders or exposed rocks 

 imbedded in the area were checked for bats and bat sign Scattered droppings were found 

 beneath 2-3 boulders near the site marked "X" in Fig. 2. 



Nun is Campground Bat activity in the campground (B Loop and entrance area) was 

 observed during the evening of 23 September The first pass by a bat was noted at 19 40 At 

 least three individuals of two species were observed foraging near treetop and lower crown 

 height (10-13 m): a species of Myotis and the larger Big-Brown or Silver-haired bat Foraging 

 rate was about 3 passes/min from 20: 10-20:43, about 1 pass/min from 20:45-21 00, and about 

 0.5 pass/min from 21 00-21 15, when observations terminated 



DISCISSION 



At least four species of bats were recorded during the survey in the Norns-Madison 

 Junction area Western Long-eared Myotis, Little Brown Myotis, Big Brown Bat. Silver-haired 

 bat Activity levels were relatively low at all sites, but this could be partly a result of the late 

 date of the surveys. Activity in the Norris and Gibbon Meadows area was lower than that 

 recorded at the lower-elevation area below Gibbon Falls to Madison Junction This did not seem 

 to be related entirely to differences in over-night temperatures. 



Foraging activity by bats at and over thermal features was low. as Martinez (1999) also 

 noted Perhaps thermal areas are not as attractive to the variety and abundance of aerial insects 

 that are fed upon by bats as are some non-thermal sites Nevertheless, maternity colonies of at 

 least two bat species (Townsend's Big-eared Bat. and a species of Myotis) have been 

 documented in thermal areas in YNP (Martinez 1999, personal communication) Similar 

 maternity sites have been reported elsewhere in western North America (eg Nagorsen and 

 Bngham 1993, West and Swain 1999) The thermal areas of YNP could support matermtv 

 colonies of several bat species and merit closer survey effort by qualified biologists and park 

 personnel 



Bats use a number of man-made structures in YNP for maternity roosts (Bogan and 

 Geluso 1999) Bridges may also be used for this purpose, but are more likely to be used as night 

 roosts Bridges throughout YNP deserve closer monitoring to determine when thev are being 

 used, by bow many individuals and species, and for what purposes Bridges could provide 

 important roosting habitat to some species in areas receiving considerable human impact As 

 bridges are repaired or replaced, they could be designed to be "bat friendly" by providing the 

 undersides with tight or secure spaces for roosting, usually on exposed steel I-beams or where 

 these are secured close to the pilings supporting the bridge The bridge design at Madison 

 Junction is distinctlv unsuitable for bats, and the elevated road span at Beryl Springs is perhaps 

 too low and accessible to predator attack to be very attractive to bats 



\n is already obvious, more inventory effort is needed in YNP to determine which 

 species of bats are present and when, what habitat features are especially attractive to them, and 



13 



