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Society for the Study of Amphibians and Reptiles
Parental Care in Dendrobates granuliferus (Anura: Dendrobatidae), with a Description of the
Tadpole
Author(s): René van Wijngaarden and Federico Bolaños
Source:
Journal of Herpetology,
Vol. 26, No. 1 (Mar., 1992), pp. 102-105
Published by: Society for the Study of Amphibians and Reptiles
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NOTES NOTES
pp. 479-517. Sandhill Crane Press, Gainesville,
Florida.
JANSEN,
D. W., AND
R. C. FOEHRING.
1983. The mech-
anism of venom secretion from Duvernoy's gland
of the snake Thamnophis
sirtalis. J. Morphol. 175:
271-277.
KARDONG,
K. W. 1982. Comparative study of changes
in prey capture behavior of the cottonmouth (Ag-
kistrodon
piscivorus)
and Egyptian cobra (Naja haje).
Copeia 1982:337-343.
MACKESSY,
S. P. 1988. Venom ontogeny in the Pacific
rattlesnakes Crotalus viridis
helleri
and C. v. oreganus.
Copeia 1988:92-101.
MCKINSTRY, D. M. 1978. Evidence of toxic saliva in
some colubrid snakes of the United States. Toxicon
16:523-534.
. 1983. Morphologic evidence of toxic saliva
in colubrid snakes: a checklist of world genera.
Herpetol. Rev. 14:12-15.
MINTON,
S. A. 1990. Venomous bites by nonven-
omous snakes: an annotated bibliography of col-
ubrid envenomation. J. Wilderness Med. 1:119-
127.
MORI,
A. 1991. Effects of prey size and type on prey-
handling behavior in Elaphe qudrivirgata.
J. Her-
petol. 25:160-166,
RODRIGUEZ-ROBLES,
J. A., AND R. THOMAS. 1992. Ven-
om function in the Puerto Rican racer, Alsophis
portoricensis (Serpentes: Colubridae). Copeia 1992
(in press).
SHINE,
R., AND
T. SCHWANER.
1985. Prey constriction
by venomous snakes: a review, and new data on
Australian species. Copeia 1985:1067-1071.
SOKAL,
R. R., AND F. J. ROHLF. 1981. Biometry, 2nd
ed. W. H. Freeman, New York. 859 pp.
TAUB,
A. M. 1967. Comparative histological studies
on Duvernoy's gland of colubrid snakes. Bull.
Amer. Mus. Nat. Hist. 138:1-50.
THOMAS, R., AND J.
A. PRIETO-HERNANDEZ.
1985. The
use of venom by the Puerto Rican snake, Alsophis
portoricensis.
Decimo Simposio de Recursos Natu-
rales 1983:13-22a.
WILLARD,
D. E. 1977. Constricting methods of snakes.
Copeia 1977:379-382.
Accepted: 15 November 1991.
Journal
of Herpetology,
Vol. 26, No. 1, pp. 102-105, 1992
Copyright 1992 Society for the Study of Amphibians and Reptiles
Parental Care in
Dendrobates granuliferus
(Anura: Dendrobatidae), with a
Description of the Tadpole
RENE VAN WIJNGAARDEN'
AND FEDERICO
BOLA1OS,2
'DLO The Winand
Staring
Centre
for Integrated
Land,
Soil
and Water
Research,
POB 125, 6700 AC Wageningen,
The
Netherlands,
and;
2Escuela de Biologia,
Universidad
de Cos-
ta Rica, San Jose, Costa Rica.
Species groups of the Neotropical frog family Den-
drobatidae can be distinguished on the basis of dif-
ferences in territorial and reproductive behavior
pp. 479-517. Sandhill Crane Press, Gainesville,
Florida.
JANSEN,
D. W., AND
R. C. FOEHRING.
1983. The mech-
anism of venom secretion from Duvernoy's gland
of the snake Thamnophis
sirtalis. J. Morphol. 175:
271-277.
KARDONG,
K. W. 1982. Comparative study of changes
in prey capture behavior of the cottonmouth (Ag-
kistrodon
piscivorus)
and Egyptian cobra (Naja haje).
Copeia 1982:337-343.
MACKESSY,
S. P. 1988. Venom ontogeny in the Pacific
rattlesnakes Crotalus viridis
helleri
and C. v. oreganus.
Copeia 1988:92-101.
MCKINSTRY, D. M. 1978. Evidence of toxic saliva in
some colubrid snakes of the United States. Toxicon
16:523-534.
. 1983. Morphologic evidence of toxic saliva
in colubrid snakes: a checklist of world genera.
Herpetol. Rev. 14:12-15.
MINTON,
S. A. 1990. Venomous bites by nonven-
omous snakes: an annotated bibliography of col-
ubrid envenomation. J. Wilderness Med. 1:119-
127.
MORI,
A. 1991. Effects of prey size and type on prey-
handling behavior in Elaphe qudrivirgata.
J. Her-
petol. 25:160-166,
RODRIGUEZ-ROBLES,
J. A., AND R. THOMAS. 1992. Ven-
om function in the Puerto Rican racer, Alsophis
portoricensis (Serpentes: Colubridae). Copeia 1992
(in press).
SHINE,
R., AND
T. SCHWANER.
1985. Prey constriction
by venomous snakes: a review, and new data on
Australian species. Copeia 1985:1067-1071.
SOKAL,
R. R., AND F. J. ROHLF. 1981. Biometry, 2nd
ed. W. H. Freeman, New York. 859 pp.
TAUB,
A. M. 1967. Comparative histological studies
on Duvernoy's gland of colubrid snakes. Bull.
Amer. Mus. Nat. Hist. 138:1-50.
THOMAS, R., AND J.
A. PRIETO-HERNANDEZ.
1985. The
use of venom by the Puerto Rican snake, Alsophis
portoricensis.
Decimo Simposio de Recursos Natu-
rales 1983:13-22a.
WILLARD,
D. E. 1977. Constricting methods of snakes.
Copeia 1977:379-382.
Accepted: 15 November 1991.
Journal
of Herpetology,
Vol. 26, No. 1, pp. 102-105, 1992
Copyright 1992 Society for the Study of Amphibians and Reptiles
Parental Care in
Dendrobates granuliferus
(Anura: Dendrobatidae), with a
Description of the Tadpole
RENE VAN WIJNGAARDEN'
AND FEDERICO
BOLA1OS,2
'DLO The Winand
Staring
Centre
for Integrated
Land,
Soil
and Water
Research,
POB 125, 6700 AC Wageningen,
The
Netherlands,
and;
2Escuela de Biologia,
Universidad
de Cos-
ta Rica, San Jose, Costa Rica.
Species groups of the Neotropical frog family Den-
drobatidae can be distinguished on the basis of dif-
ferences in territorial and reproductive behavior
(Weygoldt, 1987; Zimmermann and Zimmermann,
1988). Dendrobatesgranuliferus
Taylor 1958 is a member
of the D. histrionicus
species group (Myers and Daly,
1976, 1979; Myers et al., 1984; Zimmermann and Zim-
mermann, 1988). Insofar as known, all species in this
group (i.e., D. histrionicus,
D. lehmanni,
D. pumilio,
and
D. speciosus)
have similar advertisement calls, and so-
cial and parental behavior. Territorial behavior
(Goodman, 1971; Crump, 1972), and courtship and
mating behavior (Crump, 1972) have been described
for D. granuliferus.
In captivity, females of other species in the D. his-
trionicus
group act as nurse frogs and carry tadpoles
individually to different water-containing axils of
bromeliads. Parental care extends beyond larval
transport; females regularly deposit eggs to feed the
developing larvae (Weygoldt, 1980;
Zimmermann and
Zimmermann, 1981; Jungfer 1985).
Details of parental care are not known for D. gran-
uliferus,
but it could be assumed that parental care of
D. granuliferus
is similar to that of other species of the
D. histrionicus
group. We observed tadpole-carrying D.
granuliferus
and inspected potential tadpole deposi-
tion sites in the field to test this assumption. Herein,
we report on some aspects of parental care in D. gran-
uliferus
and describe the tadpole.
Observations were made in the Quebrada Grande,
about 2 km east of Palmar Norte, Puntarenas Prov-
ince, Costa Rica during May-November 1987 and
March-June 1988. The area is located, following the
life-zone system of Holdridge, in premontane wet
forest (basal belt transition; Tosi, 1969). The study site
included remnants of primary and secondary rain for-
est along the banks of the Quebrada. Bromeliads were
uncommon in this area, while other water containing
plants, such as palms, Heliconia
spp., and Dieffenbachia
longispatha
(Dumb cane) were abundant. Observations
of tadpole transport and deposition by D. granuliferus
were made between 0600 and 1300 h. Nurse frogs
were sexed based on the presence (male) or absence
(female) of a darkly pigmented vocal sac (Goodman,
1971). In four areas where D. granuliferus
was abun-
dant, small accumulations of water in the vegetation
were inspected for tadpoles. The volume of water
containing tadpoles was estimated by collecting the
water in a 10 ml measuring cylinder using a Pasteur
pipette. Tadpoles were measured to the nearest tenth
of a millimeter under a stereo microscope, with an
ocular micrometer. Tadpoles were deposited at the
Museo de Zoologia of the Universidad de Costa Rica,
San Jose, Costa Rica (UCR 10710), and the Nationaal
Natuurhistorisch Museum, Leiden, the Netherlands
(RMNH 24442-8).
Larval transport by female D. granuliferus
was ob-
served on eight occasions. In seven of the cases the
females carried a single tadpole; one female carried
two tadpoles. Tadpole deposition was observed four
times. Deposition sites varied: water accumulations
in a broken stem of a palm tree (0.8 m above ground);
a broken stem of a shrub (1.5 m above ground); a leaf-
axil of a Heliconia sp. (0.15 m above ground); and a
bromeliad 3.0 m above ground (Guzmania
sp.). On two
occasions a female nurse frog was seen inspecting
leaf-axils of Dieffenbachia
longispatha,
but deposition of
tadpoles in these plants was not observed. Neverthe-
less, water-containing axils of these plants were ap-
parently common deposition sites. Several females
(Weygoldt, 1987; Zimmermann and Zimmermann,
1988). Dendrobatesgranuliferus
Taylor 1958 is a member
of the D. histrionicus
species group (Myers and Daly,
1976, 1979; Myers et al., 1984; Zimmermann and Zim-
mermann, 1988). Insofar as known, all species in this
group (i.e., D. histrionicus,
D. lehmanni,
D. pumilio,
and
D. speciosus)
have similar advertisement calls, and so-
cial and parental behavior. Territorial behavior
(Goodman, 1971; Crump, 1972), and courtship and
mating behavior (Crump, 1972) have been described
for D. granuliferus.
In captivity, females of other species in the D. his-
trionicus
group act as nurse frogs and carry tadpoles
individually to different water-containing axils of
bromeliads. Parental care extends beyond larval
transport; females regularly deposit eggs to feed the
developing larvae (Weygoldt, 1980;
Zimmermann and
Zimmermann, 1981; Jungfer 1985).
Details of parental care are not known for D. gran-
uliferus,
but it could be assumed that parental care of
D. granuliferus
is similar to that of other species of the
D. histrionicus
group. We observed tadpole-carrying D.
granuliferus
and inspected potential tadpole deposi-
tion sites in the field to test this assumption. Herein,
we report on some aspects of parental care in D. gran-
uliferus
and describe the tadpole.
Observations were made in the Quebrada Grande,
about 2 km east of Palmar Norte, Puntarenas Prov-
ince, Costa Rica during May-November 1987 and
March-June 1988. The area is located, following the
life-zone system of Holdridge, in premontane wet
forest (basal belt transition; Tosi, 1969). The study site
included remnants of primary and secondary rain for-
est along the banks of the Quebrada. Bromeliads were
uncommon in this area, while other water containing
plants, such as palms, Heliconia
spp., and Dieffenbachia
longispatha
(Dumb cane) were abundant. Observations
of tadpole transport and deposition by D. granuliferus
were made between 0600 and 1300 h. Nurse frogs
were sexed based on the presence (male) or absence
(female) of a darkly pigmented vocal sac (Goodman,
1971). In four areas where D. granuliferus
was abun-
dant, small accumulations of water in the vegetation
were inspected for tadpoles. The volume of water
containing tadpoles was estimated by collecting the
water in a 10 ml measuring cylinder using a Pasteur
pipette. Tadpoles were measured to the nearest tenth
of a millimeter under a stereo microscope, with an
ocular micrometer. Tadpoles were deposited at the
Museo de Zoologia of the Universidad de Costa Rica,
San Jose, Costa Rica (UCR 10710), and the Nationaal
Natuurhistorisch Museum, Leiden, the Netherlands
(RMNH 24442-8).
Larval transport by female D. granuliferus
was ob-
served on eight occasions. In seven of the cases the
females carried a single tadpole; one female carried
two tadpoles. Tadpole deposition was observed four
times. Deposition sites varied: water accumulations
in a broken stem of a palm tree (0.8 m above ground);
a broken stem of a shrub (1.5 m above ground); a leaf-
axil of a Heliconia sp. (0.15 m above ground); and a
bromeliad 3.0 m above ground (Guzmania
sp.). On two
occasions a female nurse frog was seen inspecting
leaf-axils of Dieffenbachia
longispatha,
but deposition of
tadpoles in these plants was not observed. Neverthe-
less, water-containing axils of these plants were ap-
parently common deposition sites. Several females
102 102
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NOTES
..........
.,. ..........~
........ .
:...-.:..... .... ' . . .
A
B
FIG.
1. (A) Lateral view of the tadpole of Dendrobates
granuliferus
(stage 28, UCR 10710). (B) Mouthparts of
the tadpole of Dendrobates
granuliferus (stage 28, UCR 10710). Scale bar - 1 mm.
were found in leaf axils of D. longispatha, and seven
tadpoles were discovered in different Dieffenbachia
plants (0.6-0.95 m above ground; mean water volume
= 2.4 ml; SD = 1.4; N = 6). Together with the tadpoles,
we found two-four undeveloped eggs (three times),
and remnant egg jelly (once). Generally, only one
tadpole was found in a site (N = 10); on one occasion
two tadpoles were found together.
The following description of the tadpole of D. gran-
uliferus
is based on a single stage 28 specimen (Gosner,
1960). This specimen was selected because we wit-
nessed its deposition. It was collected from a Heliconia
plant together with three undeveloped eggs on 21
October 1987, 19 days after deposition (UCR 10710).
Body depressed (body width/body depth = 1.36);
total length (all measurements in mm) 17.8, body
length 5.8; snout rounded in dorsal and lateral pro-
files (Fig. 1A). Nostrils dorsal, directed laterally, open-
ing 0.4 behind snout; internarial distance 0.8. Eyes
dorsal, directed dorsolaterally; diameter 0.5; interocu-
lar plane 1.4 behind snout; interorbital distance 1.1.
Spiracle sinistral, low, opening 2.9 behind snout. Anal
tube medial. Caudal musculature not evident; height
adjacent to body 1.4, height at mid-tail 1.1. Tail length
67% of total length; tail height 11% of total length.
Fins equal in height; fin height 0.3 at mid-tail; dorsal
fin not extending onto body. Tip of fin attenuated.
Mouth directed anteroventrally. Oral disc not
emarginate (Fig. 1B); oral disc width 1.0. Labial teeth
in one anterior and one posterior row; tooth row for-
mula 1(1)/1 (sensu Altig, 1970). Tooth rows not ex-
tending to marginal papillae. Anterior row (A-l) with
irregularly interrupted teeth; posterior row (P-l) con-
tinuous; A-1 longer than P-1. Anterior jaw sheath
wide, forming a broad arch with slender marginal
processes; fine pointed serrations present. Posterior
jaw sheath wide, not indented; fine pointed serrations
present. Anterior jaw sheath broader than the pos-
terior. Posterior labium bordered by one row of large
marginal papillae that extend to the lateral margins
of the anterior labium; no submarginal papillae. In
life, and in preservative (formalin), the tadpole is
suffused with gray pigment, diminishing in intensity
from the dorsum to the venter; on the tail the pig-
mentation diminishes from the base to the top.
To describe ontogenetic changes in D. granuliferus
tadpoles, we collected specimens in several devel-
opmental stages (RMNH 24442-8). Except for stage 27
(N = 2), a single specimen was available for all col-
lected stages. The stage 25 specimen was collected
from the dorsum of a nurse frog; the others were from
axils of Dieffenbachia
longispatha.
Body length ranged from 3.5 (stage 25, 26) to 8.5
mm (stage 39); total length ranged from 10.5 (stage
25, 26) to 25 mm (stage 39). The ratio of body length/
body width ranged from 2.3 (stage 25) to 1.4 (stage
39). The ratio of body width/body depth varied from
1.0 (stage 25, one specimen stage 27) to 1.39 ? 0.13
(mean + SD) for the other stages. The tail comprised
67% ? 1.4% of the total length in all stages. The ratio
of tail depth/tail length was 16%
in stage 25; for the
other stages the mean of this ratio was 23% (SD =
1.5%).
Snout rounded in dorsal profile in all stages; in
lateral profile rounded in stages 26, 28, 31, 33, and
34, edge-shaped in stage 25, and truncate in stages 27
and 39. A single row of large papillae on the posterior
and lateral edges of the anterior labium (all stages).
Jaw sheath keratinization incomplete in stages 25-27;
jaw sheath edges serrated (all stages). Anterior and
posterior tooth rows keratinized in all stages. Tooth
row formula 1[1]/1. Anterior tooth row complete in
103
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NOTES
stage 25 and 26; from stage 27 onwards, A-1 irregu-
larly interrupted with a reduced number of teeth; in
stage 39, A-I divided by two gaps in a medial, and
two lateral parts. Posterior row complete in all stages.
Spiracle not visible in stages 25, 26 and 27.
Available data (Starrett, 1960; Silverstone, 1975;
Jungfer, 1985) indicate that the bodies of tadpoles of
D. pumilio and D. speciosus
are depressed, similar to
those of D. granuliferus.
In D. granuliferus,
D. histrionicus,
D. pumilio, and D. speciosus, the spiracle is low and
sinistral, the eyes and nostrils are positioned dorsally,
and the anal tube is medial. In stage 25, the tail length
accounts for 67% of the total length in D. granuliferus
and D. histrionicus,
and 63% in D. pumilio.
In stages 25-
39 of D. granuliferus,
the tail remains 67% of the total
length. In D. histrionicus
and D. pumilio,
however, the
ratio of tail length/total length decreases in relation
to increasing stage number; in stage 41 this ratio is
59% for D. histrionicus
and 53%
for D. pumilio.
Fins are
low, with attenuated (D. granuliferus,
D. speciosus)
or
rounded tips (D. granuliferus,
D. histrionicus,
D. pumilio).
In D. granuliferus,
D. histrionicus,
D. pumilio, and D.
speciosus,
the mouth is directed anteroventrally and
the oral disc is not emarginate. Jaw sheaths are ser-
rated and large rounded papillae are present on the
posterior and lateral margins of the oral disc. Labial
teeth are arranged in one anterior and one posterior
row in D. granuliferus,
D. histrionicus,
and D. pumilio;
the anterior row consists of a variable and reduced
number of more-or-less scattered teeth, while the pos-
terior row is continuous in D. granuliferus,
D. histrion-
icus, and D. pumilio (in D. pumilio the posterior row
can also be incomplete). In D. speciosus
(data available
only for one specimen, stage 32), an anterior tooth
row is lacking and the posterior row is continuous.
Because the tadpoles of the D. histrionicus
group
resemble each other closely, and since all species of
the D. histrionicus
group are allopatric, the species can
best be identified by their geographical origin. The
only sympatric congener of D. granuliferus
is D. au-
ratus.
Tadpoles of D. auratus
have two rows of smaller
papillae; the denticle formula is 2(1)(2)/3, with rows
of numerous small labial teeth (Silverstone, 1975).
Our observations indicate that, similar to other spe-
cies of the D. histrionicus
group, female D. granuliferus
carry their tadpoles to small water bodies where they
are kept fed on unfertilized eggs. Tadpoles of D. his-
trionicus,
D. lehmanni,
D. pumilio,
and D. speciosus
are
strictly oiphagous (Weygoldt, 1987). Based on our
findings of eggs and remnant egg-jelly in water bod-
ies containing tadpoles, and similarity of mouthparts,
we conclude that the feeding behavior of tadpoles of
D. granuliferus
and other species of the D. histrionicus
group is homologous.
Species of the D. histrionicus
group prefer brome-
liads as tadpole-deposition sites (Starrett, 1960; Sil-
verstone, 1973; Limerick, 1980; Weygoldt, 1987; Don-
nelly, 1989a, b). Additionally, Silverstone (1975)
reported that tadpoles of D. pumilio
were also found
in terrestrial aroids. Furthermore, we found tadpoles
of D. pumilio in broken bamboo stalks. Bromeliads
were scarce in our study site and D. granuliferus
also
used other locations for tadpole deposition (e.g., Dief-
fenbachia
longispatha).
Tadpoles of Dendrobates
granu-
liferus
were only found in small accumulations of wa-
ter, too small for the cannibalistic and larger tadpoles
of the sympatric D. auratus.
Acknowledgments.-We thank Marinus S. Hoog-
moed, Peter Leeuwangh, Peter Mudde, Douglas C.
Robinson, Brian K. Sullivan, and three anonymous
reviewers for their useful comments and valuable dis-
cussions on the manuscript. Federico Valverde did
the drawings of the tadpole, and Myrna L6pez pro-
vided the micrometer. Van Wijngaarden's trip to Cos-
ta Rica was funded by the (Dutch) Foundation for the
Advancement of Herpetology.
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M. L. 1972. Territoriality and mating be-
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granuliferus
(Anura: Dendro-
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104
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All use subject to JSTOR Terms and Conditions
NOTES NOTES
son frogs (Amphibia, Anura, Dendrobatidae). Z.
zool. Syst. Evolut.-forsch. 25:51-67.
ZIMMERMANN,
H., AND E. ZIMMERMANN. 1981. So-
cialverhalten, Fortpflanzungsverhalten und Zucht
der Farberfr6sche D. histrionicus und D. lehmanni
sowie einiger anderer Dendrobatiden. Ziet. K61-
ner Zoo. 24:83-99.
, AND . 1988. Etho-Taxonomie und zo-
ogeografische Artengruppenbildung bei Pfeilgift-
fr6schen (Anura: Dendrobatidae). Salamandra 24:
125-160.
Accepted: 15 November 1991.
Journal
of Herpetology, Vol. 26, No. 1, pp. 105-107, 1992
Copyright 1992 Society for the Study of Amphibians and Reptiles
Combat Between Rattlesnakes
(Crotalus viridis oreganus)
in the Field
MARTA J.
HERSEK,' DONALD H. OWINGS,12 and DAVID
F. HENNESSY,2
'Animal Behavior Graduate Group and;
2Department
of Psychology, University
of California,
Davis,
California
95616, USA.
Snake combat has captured the interest of many
biologists in part because of its exotic form (Bogert
and Roth, 1966; Shaw and Campbell, 1974). Among
the most spectacular fights are those of the Viperidae,
in which combatants rise up to one half of their body
length above the ground (Carpenter, 1977; Andren,
1986). The function of participating in fights has been
a matter of debate, but the favored hypothesis is that
the males are engaging in competition for females
(Bogert and Roth, 1966; Klauber, 1972; Shaw and
Campbell, 1974; Barker et al., 1979; Gillingham et al.,
1983). This hypothesis has received strong support
from Andren's (1986) field study of adders (Vipera
berus) in Sweden. Other hypotheses include compe-
tition for food (Shaw, 1951; Sutherland, 1958; Blem,
1987), territorial defense (Lowe, 1948), establishment
of dominance (Carpenter and Gillingham, 1977; Car-
penter, 1979, 1984), and rejection by males of ho-
mosexual courtship (Shaw, 1951). Snake combat has
been observed in the field (Lowe, 1948; Klauber, 1972;
Gillingham et al., 1983), and studied intensively in a
viperine species (Andren, 1986). However, most work
on pit viper (Crotalinae) combat has been done with
captive animals. We report here field observations of
eight combat episodes between northern Pacific rat-
tlesnakes (Crotalus
viridis oreganus),
six of which were
videotaped.
Our observations were made at a field site for study
of the anti-rattlesnake behavior of California ground
squirrels (Spermophilus beecheyi).
This site is located in
an abandoned walnut orchard in Camp Ohlone (Al-
ameda County, California), which is owned by the
East Bay Regional Park District (see Hennessy and
Owings, 1988, for a complete description of the site).
All observations were made from an elevated blind
(1.5 m above ground level) located on the east side
of the approximately 8100 m2 squirrel colony. North-
son frogs (Amphibia, Anura, Dendrobatidae). Z.
zool. Syst. Evolut.-forsch. 25:51-67.
ZIMMERMANN,
H., AND E. ZIMMERMANN. 1981. So-
cialverhalten, Fortpflanzungsverhalten und Zucht
der Farberfr6sche D. histrionicus und D. lehmanni
sowie einiger anderer Dendrobatiden. Ziet. K61-
ner Zoo. 24:83-99.
, AND . 1988. Etho-Taxonomie und zo-
ogeografische Artengruppenbildung bei Pfeilgift-
fr6schen (Anura: Dendrobatidae). Salamandra 24:
125-160.
Accepted: 15 November 1991.
Journal
of Herpetology, Vol. 26, No. 1, pp. 105-107, 1992
Copyright 1992 Society for the Study of Amphibians and Reptiles
Combat Between Rattlesnakes
(Crotalus viridis oreganus)
in the Field
MARTA J.
HERSEK,' DONALD H. OWINGS,12 and DAVID
F. HENNESSY,2
'Animal Behavior Graduate Group and;
2Department
of Psychology, University
of California,
Davis,
California
95616, USA.
Snake combat has captured the interest of many
biologists in part because of its exotic form (Bogert
and Roth, 1966; Shaw and Campbell, 1974). Among
the most spectacular fights are those of the Viperidae,
in which combatants rise up to one half of their body
length above the ground (Carpenter, 1977; Andren,
1986). The function of participating in fights has been
a matter of debate, but the favored hypothesis is that
the males are engaging in competition for females
(Bogert and Roth, 1966; Klauber, 1972; Shaw and
Campbell, 1974; Barker et al., 1979; Gillingham et al.,
1983). This hypothesis has received strong support
from Andren's (1986) field study of adders (Vipera
berus) in Sweden. Other hypotheses include compe-
tition for food (Shaw, 1951; Sutherland, 1958; Blem,
1987), territorial defense (Lowe, 1948), establishment
of dominance (Carpenter and Gillingham, 1977; Car-
penter, 1979, 1984), and rejection by males of ho-
mosexual courtship (Shaw, 1951). Snake combat has
been observed in the field (Lowe, 1948; Klauber, 1972;
Gillingham et al., 1983), and studied intensively in a
viperine species (Andren, 1986). However, most work
on pit viper (Crotalinae) combat has been done with
captive animals. We report here field observations of
eight combat episodes between northern Pacific rat-
tlesnakes (Crotalus
viridis oreganus),
six of which were
videotaped.
Our observations were made at a field site for study
of the anti-rattlesnake behavior of California ground
squirrels (Spermophilus beecheyi).
This site is located in
an abandoned walnut orchard in Camp Ohlone (Al-
ameda County, California), which is owned by the
East Bay Regional Park District (see Hennessy and
Owings, 1988, for a complete description of the site).
All observations were made from an elevated blind
(1.5 m above ground level) located on the east side
of the approximately 8100 m2 squirrel colony. North-
ern Pacific rattlesnakes were often observed on the
site; for example, in the spring and summer of 1986
and of 1987 we captured and marked 13 and 14 rat-
tlesnakes, respectively, on the site. At the time of the
fights reported here, however, most snakes were not
marked, and we did not determine the sex of the
participants.
Seven of the eight fights described here were ob-
served over a period of about two years, at various
times of the day during May, July, and August of 1983
and 1984; the final combat episode was observed in
May 1991. Six of the combats were videotaped; a brief
description of these follows.
On 26 May, 1983 a snake which had been marked
with red paint on the rattles a year earlier, was hunt-
ing for ground squirrel pups (Hennessy and Owings,
1988). At approximately 1425 h PST "Red Rattles"
fought with an unmarked snake for a minimum of
62 s; Red Rattles seemed to lose, in that it quickly left
the area after the fight.
On 28 July, snakes were particularly active at the
study site, engaging in at least three fights involving
at least three different snakes. At 0909 h two rattle-
snakes were in combat in tall grass for about 12 min,
15 s. At 0959 h a "Black" and a "Striped" rattlesnake
fought, also in tall grass. The encounter, which lasted
for about three min, ended with an apparent loss by
Black who crawled to a point about three m from
Striped. After they fought, both snakes were seen
moving about the area, and Black was observed
throughout the day as it crawled through the study
site. A third snake, "Large," was also moving around
the colony, and was seen to enter a squirrel burrow.
At 1655 h Black partially entered that burrow, and
immediately backed out. Large came out, and the two
fought for about three min out in the open. The fight
ended with an apparent loss by Black, who assumed
a resting coil and then crawled away. Large initially
maintained its vertical posture, and then followed
Black for about 2 m. Shortly after, Large re-entered
the burrow it apparently had successfully defended,
and was regularly seen there until 12 August. Black
entered a burrow about 6 m from Large's. The fifth
videotaped fight occurred at about 1005 h on 20 May,
1984. This episode lasted for at least 1.5 min.
On 25 May, 1991 two combat episodes occurred,
and we have partial video records for both. These
fights may have involved the same snakes, and they
may actually have been a continuation of one long
interaction (if so, the snakes were out of sight for
about 30 min in between the observed combat epi-
sodes). Two snakes fought in a woodpile at 1300 h,
for approximately one min; about 30 min later two
snakes were observed fighting in a squirrel burrow
six m from the woodpile. The second episode lasted
for at least 20 min. As one snake was retreating at the
end of the fight, observers captured both and verified
that they were males.
Two observed combat episodes were not video-
taped; these occurred on 26 July, 1982 at 1900 h, and
at 1019 h on 18 August, 1983. For neither of these
combats was a minimum duration recorded.
Two of our video records were sufficiently clear to
permit detailed quantitative description. Although the
snakes were not marked, differences in size or skin-
patterning allowed the participants to be distin-
guished. The most conspicuous features of these com-
ern Pacific rattlesnakes were often observed on the
site; for example, in the spring and summer of 1986
and of 1987 we captured and marked 13 and 14 rat-
tlesnakes, respectively, on the site. At the time of the
fights reported here, however, most snakes were not
marked, and we did not determine the sex of the
participants.
Seven of the eight fights described here were ob-
served over a period of about two years, at various
times of the day during May, July, and August of 1983
and 1984; the final combat episode was observed in
May 1991. Six of the combats were videotaped; a brief
description of these follows.
On 26 May, 1983 a snake which had been marked
with red paint on the rattles a year earlier, was hunt-
ing for ground squirrel pups (Hennessy and Owings,
1988). At approximately 1425 h PST "Red Rattles"
fought with an unmarked snake for a minimum of
62 s; Red Rattles seemed to lose, in that it quickly left
the area after the fight.
On 28 July, snakes were particularly active at the
study site, engaging in at least three fights involving
at least three different snakes. At 0909 h two rattle-
snakes were in combat in tall grass for about 12 min,
15 s. At 0959 h a "Black" and a "Striped" rattlesnake
fought, also in tall grass. The encounter, which lasted
for about three min, ended with an apparent loss by
Black who crawled to a point about three m from
Striped. After they fought, both snakes were seen
moving about the area, and Black was observed
throughout the day as it crawled through the study
site. A third snake, "Large," was also moving around
the colony, and was seen to enter a squirrel burrow.
At 1655 h Black partially entered that burrow, and
immediately backed out. Large came out, and the two
fought for about three min out in the open. The fight
ended with an apparent loss by Black, who assumed
a resting coil and then crawled away. Large initially
maintained its vertical posture, and then followed
Black for about 2 m. Shortly after, Large re-entered
the burrow it apparently had successfully defended,
and was regularly seen there until 12 August. Black
entered a burrow about 6 m from Large's. The fifth
videotaped fight occurred at about 1005 h on 20 May,
1984. This episode lasted for at least 1.5 min.
On 25 May, 1991 two combat episodes occurred,
and we have partial video records for both. These
fights may have involved the same snakes, and they
may actually have been a continuation of one long
interaction (if so, the snakes were out of sight for
about 30 min in between the observed combat epi-
sodes). Two snakes fought in a woodpile at 1300 h,
for approximately one min; about 30 min later two
snakes were observed fighting in a squirrel burrow
six m from the woodpile. The second episode lasted
for at least 20 min. As one snake was retreating at the
end of the fight, observers captured both and verified
that they were males.
Two observed combat episodes were not video-
taped; these occurred on 26 July, 1982 at 1900 h, and
at 1019 h on 18 August, 1983. For neither of these
combats was a minimum duration recorded.
Two of our video records were sufficiently clear to
permit detailed quantitative description. Although the
snakes were not marked, differences in size or skin-
patterning allowed the participants to be distin-
guished. The most conspicuous features of these com-
105 105
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