All other snake
models were readily attacked implying that aposematic coloration
is a deterrent to this species. Observations indicate that Blue-crowned
Motmots (Momotus momota) at the National Aquarium consume several
species of poison dart frogs including the black-and-green poison
dart frog (Dendrobates auratus) and phantasmal poison dart frog
(Dendrobates tricolor). However, these frogs were raised in captivity
and either do not produce or have relatively low levels of the characteristic
skin toxins (Kricher 1997; C. Rowsom, pers. comm.).
At approximately
9:30 CST on 26 March 1995, an adult Rufous Motmot was observed in
secondary lowland tropical forest from a hiking trail located at
Estacion Biological La Suerte, near Cariari, Limon Province, north-eastern
Costa Rica (10º 26' N, 83º 46' W). The bird landed 25
m from the trail on an exposed perch 3m above the ground and was
easily observed for approximately 4 min. After 4 min. another individual
landed on the same branch next to the first individual. The newly
arrived motmot was carrying a black-and-green poison dart frog in
its beak which it fed immediately to the first individual. It is
not possible to distinguish between sexes in Rufous Motmots; however,
their behavior was intrepreted as a male who was feeding the female
as a courtship gesture. Both individuals had diagnostic black breast
marks and raquetails indicative of adult birds, suggesting that
this was probably not a fledgling being fed. The pair continued
sitting on the brance for approximately 30 min. after which they
flew off together into the forest. Neither individual appeared to
suffer any ill effects from either grasping or consuming the poison
dart frog.
The typical
diet of motmots varies somewhat in conjunction with body size. Smaller
species prefer insects while larger species consume insects along
with other invertebrates, small vertebrates and fruit (Orejuela
1980, Remsen et al. 1993). The Rufous Motmot consumes arthropods,
other invertebrates including crabs, small vertebrates including
fish, lizards and birds, as well as fruit (Remsen et al. 1993).
Frogs have been reported as a dietary component of tyhe Rufous,
Broad-billed (Electron platyrhynchum) and Turquoise-browed motmots
(Remsen et al. 1993), and Blue-crowned Motmots in captivity (C.
Rowsom, pers. comm.).
The effect of
poison dart frog toxins on various potential predators has received
relatively little attention. Brodie and Tumbarllo (1977) tested
the response of garter snakes (Thamnophis sirtalis) to D. auratus
offered as prey. Snakes readily mouthed, or in some cases consumed
the frogs but all exhibited head shaking, mouth opening, convulsions,
and loss of equilibrium. Only one snake actually died and that was
after consuming its third frog. These snakes do not possess color
vision andmight not be influenced by the aposematic coloration to
the extent that an organism with color vision would be (Brodie and
Tumbarello 1977).
While motmots
in general may be warned by aposematic coloration, the Rufous Motmot
at least is capable of handling and consuming this particular species
of poison dart frog. Dendrobates auratus reaches densities of 1
individual / 180m2 in. one locality at La Suerte known to be frequented
by Rufous Motmots (B. Gravs, pers. comm.) One pair was observed
on the ground rummaging through leaf litter where they would undoubtedly
encounter D. Auratus (B. Graves, pers. comm.). The level of toxins
in the frogs of this area, how the motmots physiologically handle
the toxins, and the frequency with which they consume D. auratus
remain unknown.
AKNOWLEDGEMENTS
I would like to thank Dr. T. LaDuke of East Stroudsburg University,
Dr. B. Graves of Northern Michigan University, and C. Rowsom of
the National Aquarium in Baltimore for encouragement and assistance
with this manuscript.
LITERATURE CITED
Brodie, E.D. and M.S. Tumbarello. 1977. The antipredator functions
of Dendrobates auratus (Amphibia, Anura, Dendorbatidae) skin secretions
in regard to a snake predator. J. Herp 12:264-265
Kricher, J. 1977. A Neotropical companion. Princeton Univ. Press.,
New Jersey.
Orejuela, J.E.
1980. Niche relationships between Torquiose-browed and Blue-crowned
motmots. Wilson Bull. 92:229-244.
Remsen, J.V.,
A. Hyde, and A. Chapman. 1993. The diets of Neotropical trogons,
motmots, barbets and toucans. Condor 95:178-192
Smith, S.M.
1975. Innate recognition of coral snake pattern by a possible avian
predator. Nature (Lond.) 187:759-760.
Published in Wilson Bulletin III(3): 438-439
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