Food habits of male bird-voiced treefrogs, Hyla avivoca

-107­
FOOD HABITS OF MALE BIRD-VOICED TREEFROGS,
HYLA AVIVOCA (ANURA: HYLIDAE), IN ARKANSAS
DAVID
H.
JAMIESON, STANLEY
AND CHRIS
E.
TRAUTH,
T. McALLISTER
Department of Biological Sciences. Arkansas State University,
State University. Arkansas 72467 and Renal-Metabolic Laboratory (/51-G).
Department of Veterans Affairs Medical Center,
4500 S. Lancaster Road, Dallas. Texas 75216 (CTM)
ABSTRACT.-We analyzed stomach contents of 56 male bird-voiced treefrogs, Hyla avivoca
Viosca, 1928, collected in late spring and early summer 1991 from sites in central Arkansas.
Ants and beetles were the predominant prey items; the next most abundant group was
caterpillars. Ants of the genus Cremastogaster were the most common food source. Several
ground-dwelling arthropods found in the diet of other species of Hyla were noticeably absent
from the diet of H. avivoca. Our data suggest that calling male H. avivoca forage largely
on tree-dwelling insects when compared to sympatric Hyla, and this mode may be a reflection
of habitat preference and prey availability rather than prey selection. Key words: ants;
arthropods; insects; bird-voiced treefrog; Hyla avivoca; food habits; diet.
The bird-voiced treefrog, Hyla avivoca Viosca, 1928, has a sporadic and
poorly-documented distribution in three states (Arkansas, Louisiana, and
Oklahoma) from which the species is known west of the Mississippi River
(Smith, 1966; Dundee and Rossman, 1989; Conant and Collins, 1991).
Recent investigations by Trauth and Robinette (1990a, 1990b) into the
distribution and life history of Arkansas populations have revealed this
frog to be more common in the state than previously understood. The
species generally inhabits large rivers, headwater swamps, and swampy
floodplains and lakes in Arkansas. Although much has been documented
about the natural history and ecology of other Hyla species, little ecological
data are available for bird-voiced treefrogs, and nothing, to our knowledge,
is known about the diet of H. avivoca.
The diet of gray treefrogs, Hyla versicolor LeConte, 1825, and H.
chrysocelis Cope, 1880 (considered by some to be the closest living relatives
of H. avivoca), was investigated in Texas by Ralin (1968). He reported
that both species fed extensively on click beetles (Coleoptera: Elateridae)
and harvester ants (Pogonomyrmex). He also concluded that both species
fed not only while perched on the bark and foliage of trees, but also, to
some extent, on the ground. Interestingly, harvester ants are not known
to occur in trees; rather, they are especially common in cultivated fields
and bare sandy areas near roads. In addition, other insect orders found
in stomachs included grasshoppers (Orthoptera-only in H. versicolor),
flies (Diptera), and caterpillar larvae (Lepidoptera). Brown (1974) studied
the food habits of several anurans from southeastern Arkansas. He found
that green treefrogs, H. cinerea (Schneider, 1792), primarily fed on insects
found on the leaves of plants and included leafhoppers (Homoptera:
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THE TEXAS JOURNAL OF SCIENCE-VOL. 45, NO. I, 1993
Cicadellidae), acridid grasshoppers, caterpillars, leaf beetles
(Chrysomelidae), and spiders (Arachnida). HyJa cinerea consumed
mosquitoes (Diptera: Culicidae) and houseflies (Muscidae) in laboratory
experiments (Freed, 1980). Freed also reported that prey selection was
dependent upon prey species activity rather than size of prey. In a field
study, Freed (1982) reported that H. cinerea consumed mostly noctuid
caterpillars, cantharid beetle larva, and, to a lesser extent, field crickets
(Orthoptera: Gryllidae) and stink bugs (Hemiptera: Pentatomidae).
The purposes of our study are to describe feeding patterns for calling
male H. avivoca from central Arkansas and compare our results with what
is known of diet in other arboreal treefrogs.
MATERIALS AND METHODS
Fifty-six adult and juvenile male H. avivoca were collected from six localities in four counties
(Conway, Faulkner, Grant, and Monroe) of central Arkansas' from late May through mid­
July, 1991. All frogs were taken from breeding colonies at dusk or after dark as they called
several meters above water from trees (primarily cypress-tupelo gums) and buttonbush shrubs
(Cephalanrhus). Specimens were placed in plastic bags on ice following capture and processed
within 24 hours in the laboratory at Arkansas State University (ASU). Frogs were killed
in a dilute chloretone solution and fixed in 10 percent formalin for 48 hours prior to examination.
Stomachs were removed and stored in individual vials containing 70 percent ethanol. Food
items were removed, counted, and identified using a binocular dissecting microscope and
dichotomous keys provided in Creighton (1950), Cook (1953), and Borrer et al. (1989). A
food item consisted of a whole specimen or parts representing a whole specimen. Whenever
possible, insect taxa were identified to family. Prey availability was not assessed quantitatively;
however, some qualitative assessment was made by collecting and observing arthropods in
each study area. Voucher specimens of H. avivoca are deposited in the ASU Herpetological
Museum (nos. 17766; 17770-77; 17787-88; 17799-17834; 17860-67).
RESULTS AND DISCUSSION
Of the 56 stomachs examined, 51 (91 percent) contained food items.
There was an average of 3.9 food items per stomach (range one to 14).
The total number and percent occurrence of food items are given in Table
1. Ants (Hymenoptera: Formicidae) and beetles (Coleoptera) were the
predominant prey items; the next most abundant group was lepidopteran
larvae. Of the 75 identifiable ants, 72 (96 percent) were Cremastogaster
workers ranging from 2.5 to 4.0 mm in length. According to Cook (1953),
these ants often nest under the bark of trees and can be recognized by
the unique way they climb trees in straggling files. Ant collections made
at one locality revealed that Cremastogaster workers were common on the
bark and foliage of trees in a cypress-tupelo swamp. As many as 14
Cremastogaster were found in a single stomach and several stomachs
contained only Cremastogaster. Although ant trails were observed on the
surfaces of several overhanging tree limbs, it was not determined whether
these ants were being consumed as they crawled near the frogs or whether
the frogs actively pursued them. Duellman and Trueb (1986) suggested
FOOD HABITS OF HYLA AVIVOCA
47
TABLE I. Percent occurrence and total number of food items from stomachs of male Hyla
avivoca from Arkansas.
Taxa
Arachnida
Acarina
Araneae
Insecta
Unidentifiable
Coleoptera
Cantharidae
Carabidae
Coccinellidae
Cucujidae
Elateridae
Unidentifiable
Hemiptera
Reduviidae
Homoptera
Cicadellidae
Hymenoptera
Formicidae
CremaslOgas/er
Campono/us
Unidentifiable
Lepidoptera
Geometridae (larvae)
Unidentifiable (larvae)
Unidentifiable (adult)
Odonata
Zygoptera
Unidentifiable
Psocoptera
Percent
occurrence
in stomachs
(N= 51)
Total number of
food items
5.4
1.8
8
I
7.1
4
1.8
1.8
I
I
5
3
3
5
9.0
5.4
5.4
9.0
1.8
1.8
39.3
5.4
28.6
72
3
36
3.6
9.0
2
5
1
1.8
1.8
3.6
I
4
that some ant specialists, particularly several microhylid species, locate ant
trails by olfaction. The frogs may then "sit and wait" to capture ants as
they pass by. Although the method of ant capture by H. avivoca remains
unclear, the large number of ants in several stomachs suggest that H. avivoca
may sit motionless near ant trails and consume individuals of Cremastogaster
as they parade by in their characteristic straggling files. However, frogs
• might locate and raid ant nests under the bark of trees. Our data do not
distinguish between these alternatives.
Coccinellids were the most frequently encountered beetles followed by
cucujids and elaterids. Coccinellids (ladybird beetles) are predaceous and
are abundant on aphid-infested vegetation whereas cucujids (flat bark
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THE TEXAS JOURNAL OF SCIENCE-VOL. 45, NO. I, 1993
beetles) occur on and under the bark of trees where they feed on mites
and other small insects (Borrer et aI., 1989). Ralin (1963) stated that elaterids
(click beetles) are generally arboreal and concluded that H. chrysoscelis
was a more arboreal feeder than H. versicolor based on a higher percent
occurrence of elaterids in the diet of H. chrysoscelis.
Unfortunately, because lepidopteran larvae are soft-bodied and digested
quickly, few in our sample were identifiable to family. Lepidopteran larvae
were encountered in 11 percent of the stomachs of H. avivoca compared
to 15 percent reported by Freed (1982) for H. cinerea and 21 percent and
14 percent for H. chrysoscelis and H. versicolor, respectively (Ralin, 1968).
The presence of barklice (Psocoptera) and flat bark beetles indicate that
H. avivoca spends some time feeding on insects that occur in the tree­
bark crevice microhabitat. Unlike H. avivoca, these insects were not
consumed by H. cinerea, H. chrysoscelis, or H. versicolor (Brown, 1974;
Freed, 1982).
There was a conspicuous absence of ground-dwelling arthropods in the
diet of H. avivoca when compared to other Hyla species. Moreover, data
from Table 1 suggest that during the study period, H. avivoca rarely, if
ever, fed on the ground. This feeding mode may be a reflection of habitat
preference rather then prey selection. Unlike H. chrysoscelis, H. cinerea,
and H. versicolor (all of which are found in a myriad of habitats), H.
avivoca seems to be restricted to old-growth, cypress-tupelo swamps or
similar aquatic habitats in Arkansas. Because of the permanent-water
situation associated with these environments, H. avivoca would have to
leave the site (or, at least, the inundated areas) in order to encounter ground­
dwelling insects. Thus, calling males appear to have a foraging tactic that
precludes movement away from breeding perches or sites. During the
breeding season, calling males appear to specialize on arboreal insects in
central Arkansas. However, the diet of calling male frogs may not be typical
of the population in general that does not approach a maintenance diet.
Thus, additional study utilizing female H. avivoca and males collected
outside the breeding season is certainly warranted.
ACKNOWLEDGMENTS
We thank J. W. Robinette for field assistance and the Arkansas Game and Fish Commission
for Scientific Collecting Permits nos. 34 and 1114 to Trauth and McAllister, respectively.
This study was funded by a grant (F90-3) from the Arkansas Nongame Preservation Committee
to Trauth.
LITERATURE CITED
Borror, D. J., C. A. Triplehorn, and N. F. Johnson. 1989. An inlroduction to Ihe sludy
of insects. Saunders College Publ., Philadelphia, 875 pp.
Brown, R. L. 1974. Diets and habitat preferences of selected anurans from southeasl Arkansas.
Amer. Midland Nat., 91:468-473.
FOOD HABITS OF HYLA AVIVOCA
49
Conant, R., and J. T. Collins. 1991. A field guide to reptiles and amphibians of eastern
and central North America. Houghton Mifflin Co., Boston, 3rd ed., 450 pp.
Cook, T. W. 1953. The ants of California. Pacific Books, Palo Alto, 391 pp.
Creighton, W. S. 1950. The ants of North America. Bull. Mus. Compo Zool., 104:1-569.
Duellman, W. E., and L. Trueb. 1986. Biology of amphibians. McGraw-Hill, New York,
670 pp.
Dundee, H. A., and D. A. Rossman. 1989. The amphibians and reptiles of Louisiana. Louisiana
State Univ. Press, Baton Rouge, xi + 300 pp.
Freed, A. N. 1980. Prey selection and feeding behavior of the green treefrog (H. cinerea).
Ecology, 61:461-465.
- - . 1982. A treefrogs menu: selection for an evenings meal. Oecologia, 53:20-26.
Ralin, D. B. 1968. Ecological and reproductive differentiation in the cryptic species of the
Hyla versicolor complex (Hylidae). Southwestern Nat., 13:283-300.
Smith, P. W. 1966. Hyla avivoca. Cat. American Amph. Rept., 28.1-28.2.
Trauth, S. E., and J. W. Robinette. 1990a. Notes on distribution, mating actiVIty, and
reproduction in the bird-voiced treefrog, Hyla avivoca, in Arkansas. Bull. Chicago Herpetol.
Soc., 25:218-219.
- - . 1990b. Geographic distribution: Hyla avivoca (Bird-voiced Treefrog). Herpetol. Rev.,
21:95.