Tables
Box 1: Identification key for Sumatran bats occurring in oil
palm plantations, based on categorical and relative morphological and
acoustic features. The key is adapted to the current quality of
near-infrared imagery obtained from bat point counts. The species list
is based on our own checklist of bats sampled using mist nets in oil
palm plantations (Darras, unpublished data). Fmax = frequency of maximal
(i.e., peak) frequency.
- We discriminate Pteropodidae from other bat families based on their
morphological adaptation and behavior.
- Pteropodidae have visibly enlarged eyes with a retroreflective layer
(tapetum lucidum) to see in very low light levels
(Müller et al.,
2007; Ollivier et al., 2004). Their intrafemoral membrane and tail
are inconspicuous, and they have a straighter flight compared to
insectivorous bats that maneuver to hunt (pers. obs.). →2
- Echolocating bats have characteristically small eyes, as they rely
primarily on their auditory sense to navigate and forage. →5
- We check the relative snout size using the head length (from back to
snout tip) to head width (from throat to top) ratio:
- Relatively short (ratio < 1.7) and robust snout →3
- Relatively long (ratio ≥ 2) and narrow snout→4
- We check for diagnostic features of different pteropodid genera:
- Whitish digits (adult Cynopterus)
- Spotted wings (Balionycteris maculata)
- Black-capped head (Chironax)
- None of the above (Megaerops/juvenile Cynopterus)
- We check for the overall body size by comparison with photographed
habitat features:
- Very large (Pteropus)
- Intermediate or small (Eonycteris/Rousettus/Macroglossus)
- We distinguish echolocating families based on the relative size of the
ears. Large ears are characteristic for bats passively listening for
prey and are used to amplify the received ultrasound echoes
(Obrist et al.,
1993).
- Ears approximately as large as the head, FM calls (Nycteridae,
Megadermatidae) →6
- Ears about half as large as the head or smaller →7
- We use the tail to discriminate between both families:
- Interfemoral membrane obvious, tail inconspicuous, Fmax 58 kHz
(Megaderma spasma)
- Both interfemoral membrane and tail obvious, Fmax 97 kHz
(Nycteris tragata)
- Further, we distinguish several families from their tail and
interfemoral membrane shape:
- Interfemoral membrane small, tail shorter than hind feet, ears half
as large as head, nostrils open roughly perpendicularly to the open
mouth, CF calls (Rhinolophus, Hipposideros) →8
- Interfemoral membrane small but notable, tail inconspicuous
(Coelops)
- Obvious tail extending from the interfemoral membrane (Molossidae,
Emballonuridae, Rhinopomatidae)
- Tail enclosed in obvious interfemoral membrane, ears less than one
third of the head, snout direction points in similar direction as
the mouth (Vespertilionidae, Miniopteridae) →9
- Several species can be distinguished from their calls’ frequency of
maximum energy:
- Fmax 78 kHz (Hipposideros orbiculus)
- Fmax 137 kHz (Hipposideros kunzi)
- Fmax 65 kHz (Rhinolophus sedulus)
- Fmax 54 kHz (Rhinolophus trifoliatus)
- Vespertilionidae and Miniopteridae can be distinguished from the
relative sizes of the phalanges of the third digit.
- First phalange <40% of second phalange (Miniopteridae)
- First phalange about as long as second phalange (Vespertilionidae)