CHARLES W. MTE

and A. STANLEY RA

Checklist of

Amphibians and

Reptiles of Barro

Colorado Island, Panama,

V With Comments on

FaunaJ Change

and Sampling

SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • 1969 NUMBER 10

SMITHSONIAN CONTRIBUTIONS TO

ZOOLOGY

NUMBER 10

Charles w. Myers Checklist of Amphibians

and A. Stanley Rand ^ d Reptile s o f

Barro Colorado Island,

Panama, with Comments

on Faunal Change

and Sampling

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ABSTRACT

One hundred species of amphibians (32) and reptiles (68) are estimated to occur

on Barro Colorado Island, on the basis of approximately 47 years of collecting. The

island is a seasonally wet, tropical forest locality in man-made Gatun Lake, central

Panama. The faunal composition has not been static since the island's formation

in 1912-1914. Some species have disappeared from the island whereas some others

seem to be recent arrivals. Faunal change is at least partly correlated with vegetational

succession, as old clearings change toward mature forest. The extirpation of certain

"edge" species and their failure to have recolonized the laboratory clearing indicates

that it is easier for a resident population to become extinct than for new colonization

to occur. The sampling of such a complex, tropical herpetofauna is shown to be not

so difficult as might be expected. Man-hours of collecting are plotted against percent

of the herpetofauna for several collections, indicating that nearly one-half of the

species can be collected in a few weeks of intensive effort in the rainy season. Approximately 80 percent of the species recorded from the island had been collected by 1931,

after only about a decade of sporadic, unsystematic collecting by various persons. The

generalization that tropical species have lower population densities than temperate

species may not be valid for such groups as frogs and lizards but does seem true of

snake faunas in low, humid forest regions. Snakes also are more difficult to collect

in the tropics because of shifts in habits. There is a great expansion of tropical snakes

into arboreal situations and a general avoidance (by all vertebrates) of rock and log

microhabitats, which are frequently occupied by large arachnids. Small terrestrial

snakes of lowland tropical forests tend either to be fossorial or to inhabit the leaf

litter, where they are difficult to detect. Seasonal aggregations of snakes are rare

in the wet tropics.

Recent years have brought a greatly increased use

of Barro Colorado Island by ecologists, physiologists,

and other nontaxonomists, thus creating a need for

lists of the currently accepted names of local animals.

The present checklist of amphibians and reptiles brings

up to date the nomenclature and included species of

earlier lists (Dunn, 1931a, 1931b, 1949; Zetek, 1951),

and also indicates departures in nomenclature from

other papers, including Allee (1926), Allee and Torvik

(1927), and Netting (1936).

One hundred species of amphibians and reptiles are

estimated to occur in this forested area of less than six

square miles. This count probably is the most complete

available of the herpetofauna of any humid locality on

Charles W. Myers, Department of Herpetology, The American

Museum of Natural History, New York, New York 10024.

A. Stanley Rand, Smithsonian Tropical Research Institute,

Box 2072, Balboa, Canal Zone.

a tropical mainland, and is the result of collecting

efforts of a number of persons over several decades. By

reason of its relative completeness, the present list

should be useful as a means of comparing the amphibian and reptile faunas of other areas less well known.

In concluding paragraphs, we comment briefly on

faunal changes and abundance and demonstrate that

a fauna even as large and complex as this one can be

effectively sampled within reasonable time limits.

Barro Colorado (9° 10' North Latitude) is a former

hilltop and the largest island in Gatun Lake, which

was formed by the dredging of the Panama Canal and

the damming of the Chagres River in 1912. The island

is approximately 3600 acres in area (about 14.5 square

kilometers), hilly, and has a maximum elevation of

452 feet above Gatun Lake, or 537 feet (164 meters)

above sea level. Surface drainage is by small, clearwater streams with rocky beds that dry to isolated pools

1
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

near the end of most dry seasons. There is a small, upland swampy area near the center of the island. Except

for two small, maintained clearings, the island is covered by forest stands of various ages, the youngest and

least extensive being of about 25 years and the oldest

of unknown age but still showing traces of disturbance

by the human animal. The forest can be classified

broadly according to any of several systems, i.e., tropical monsoon forest (Koppen's climatic classification),

tropical moist forest (Holdridge's life zone classification), or intermediate between evergreen and semievergreen seasonal forests (Beard's climax classification) . The annual rainfall averages 106.91 inches

(76.57-143.42 inches, 1925-1965). A well-differentiated dry season occurs from about the end of December into April; average rainfall during the period

January-April is 8.22 inches (1.20-26.64 inches) and

two months each average less than 2 inches. A map

showing physiognomic aspects of the vegetation is

found in Bennett (1963), and various photographs of

the forest are given in Kenoyer's account of vegetational succession (1929). A view of the laboratory

clearing and surrounding forest is appended to Woodring's geological reconnaissance of the island (1958,

pi. 2).

In the list that follows, an asterisk (*) before a name

means that in our experience, the species is relatively

common in the proper habitat. A dagger (f) denotes

a species thought to be unusually rare, but there are

certainly other rare species, especially snakes, not so

indicated. The phrase "type-locality" after a name

means that the name is based on a specimen (the

holotype) collected on Barro Colorado Island. Except

for the frog Phrynohyas (q.v.), those species added

since the publication of Zetek's list (1951) are represented by specimens in the American Museum of Natural History (AMNH), the United States National

Museum (USNM), or the University of Kansas Museum of Natural History (KU) ; the depository is noted

by the initials following the name of the species. Barbour (1925, p. 11) foresaw that, "It will be years

before the herpetological possibilities of the island are

adequately investigated, and much strictly systematic

work will be necessary before students of life histories

will be certain of the species which they are observing." In the course of progress toward taxonoinic stability (an illusive goal save in the relative sense) it is

natural that many names in the literature of Barro

Colorado are different from those presently used; such

names may be synonyms, misidentifications, or misspellings and, if substantially different, are shown in

parentheses behind names now considered valid. We

have not been completely consistent in our treatment

of subspecies, omitting available trinomials in some

cases where intraspecific variation is not or only poorly

known, but other times inserting them for no other

reason than that the name is well established in the

Panamanian literature. We consider the designation

of subspecies to be of dubious value and a frequent

hindrance to thorough variational analysis.

Amphibia (32)

Gymnophiona (1)

Oscaecilia ochrocephala (Cope) (Caecilia ochrocephala)

Caudata (2)

Oedipina complex (Dunn) (Oedipus complex, O.

simplex, Oedopinola complex)

Oedipina parvipes (Peters) (Oedipus parvipes,

Oedopinola parvipes)

Salientia (29)

LEPTODACTYLIDAE

Eleutherodactylus biporcatus (Peters)

*Eleutherodactylus bufoniformis (Boulenger) (? E.

rugulosa)

Eleutherodactylus cruentus (Peters)—application of

name uncertain

* Eleutherodactylus diastema (Cope)

* Eleutherodactylus fitzingeri (Schmidt) (E. fleischmanni, E. palmatus)

^Eleutherodactylus gaigeae (Dunn) (Lithodytes

gaigei)

Eleutherodactylus longirostris (Boulenger)

Eleutherodactylus molinoi (Barbour)—type-locality;

(E. lutosus molinoi, Syrrhopus molinoi)

* Eleutherodactylus ockendeni (Boulenger)—application of name uncertain

*Engystomops pustulosus (Cope) (E. ruthveni)

Leptodactylus insularum Barbour (L. bolivianus)

*Lcptodactylus pentadactylus (Laurenti)

BUFONIDAE

*Bufo marinus (Linnaeus)

*Bufo typhonius alatus Thominot
NUMBER 10

DENDROBATIDAE

*Dendrobates auratus (Girard) {D. tinctorius)

*Colostethus nubicola flotator (Dunn)—type-locality;

{Phyllobates "near latinasus and talamancae," P.

flotator, P. nubicola flotator)

HYLIDAE

*Hyla boulengeri (Cope)

*Hyla phlebodes Stejneger {H. underwoodi)

*Hyla rufitela Fouquette—type-locality; {H. albomarginata)

^Agalychnis calcarifer (Boulenger) {Phyllomedusa

calcarifer)

*Agalychnis callidryas (Cope) {Phyllomedusa callidryas)

Agalychnis spurrelli (Boulenger) {Agalychnis dacnicolor, Phyllomedusa dacnicolor)

•fPhrynohyas venulosa (Laurenti) {Hyla venulosa)

fSmilisca phaeota (Cope) {Hyla phaeota)

*Smilisca sila Duellman and Trueb {Hyla gabbii, H.

sordida)

CENTROLENIDAE

* Centrolenella fleischmanni (Boettger) {Centrolene

fleischmanni)

Centrolenella prosoblepon (Boettger) {Centrolene

prosoblepon)

Centrolenella spinosa Taylor {Centrolene parambae,

C. pulveratum)

RANIDAE

Rana palmipes Spix AMNH, KU

Reptilia (68)

Testudines (5)

^Chelydra acutirostris Peters

Geoemyda annulata (Gray) {Rhinoclemmys gabbii)

jGeoemyda funerea (Cope)

Kinosternonleucostomum (DumerilandBibron) {K.

postinguinale)

*Pseudemys scripta ornata (Gray) (P. ornata)

Crocodilia (2)

*Caiman crocodilus fuscus (Cope)

*Crocodylus acutus Cuvier

Sauria (22)

IGUANIDAE

Anolis auratus Daudin {Norops auratus)

Anolis biporcatus {Wiegmann) {A. copei)

Anolis capito Peters

*Anolis frenatus Cope {A. longipes, a name that is

technically a synonym of A. capito)

* Anolis limifrons Cope

fAnolis lionotus Cope

Anolis pentaprion Cope

Anolis vittigerus Cope {A. lemurinus, A. sallaei)

*Basiliscus basiliscus (Linnaeus)

Corythophanes cristatus (Merrem)

*Iguana iguana iguana (Linnaeus)

Polychrus gutturosus Berthold

GEKKONIDAE

Thecadactylus rapicauda (Houttuyn)

SPHAERODACTYLIDAE

Gonatodes albogularis fuscus (Hallowell)

Lepidoblepharis sanctaemartae fugax Ruthven—

type-locality

Sphaerodactylus lineolatus Lichtenstein and von

Martens

XANTUSIIDAE

Lepidophyma flavomaculatum obscurum Barbour

TEIIDAE

*Ameiva festiva (Lichtenstein and von Martens)

*Ameiva leptophrys Cope {A. ameiva, A. undulata)

fLeposoma southi Ruthven and Gaige

SCINCIDAE

*Mabuya mabouya (Lacepede)—application of name

uncertain; (A/, agilis)

AMPHISBAENIDAE

Amphisbaena fuliginosa Linnaeus

Serpentes (39)

ANOMALIPIDIDAE

Anomalepis dentata Taylor—type-locality; {A. mexicanus)

Liotyphlops albirostris (Peters) USNM

BOIDAE

*Boa constrictor imperator Daudin

Corallusannulatus (Cope) KU

Epicrates cenchria maurus Gray
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

COLUBRIDAE

Amastridium veliferum Cope

Chironius carinatus (Linnaeus) (Erpetodryas carinatus)

Chironius grandisquamis (Peters) (C. fuscus, C.

melas)

*Coniophanes fissidens (Giinther) (C. punctigularis)

*Dendrophidion percarinatus (Cope) (D. dendrophis,

Drymobius dendrophys)

*Dryadophis melanolomus alternatus (Bocourt) (Drymobius boddaertii)

Drymarchon corais melanurus (Dumeril, Bibron, and

Dumeril) KU

Enulius flavitorques (Cope)

Enuliussclateri (Boulenger) (Leptocalamus sclateri,

E. slateri)

*Imantodescenchoa (Linnaeus)

"flmantodes gemmistratus (Cope) (/. elegans)

*Leimadophis epinephalus epinephalus (Cope) (Liophis epinephelus)

Leptodeira annulata rhombifera Giinther

Leptodeira septentrionalis ornata (Bocourt) (L. a.

annulata)

Leptophis ahactulla occidentalis (Giinther) (Thalerophis richardi occidentalis)

Ninia maculata maculata (Peters) AMNH, USNM

*Oxybelis aeneus aeneus (Wagler) (O. acuminatus)

Oxyrhopus petola sebae Dumeril, Bibron, and

Dumeril

Pliocercus euryzonus dimidiatus Cope (Urotheca

dimidiata)

Pseudoboa neuwiedii (Dumeril, Bibron, and

Dumeril) USNM

Pseustes poecilonotus shropshirei (Barbour and

Amaral) (Phrynonax poecilonotus)

Rhadinaea decorata (Giinther) (Liophis decoratus)

Rhadinaea pachyura julviccps Cope {Liophis pachyurus)

Siphlophis cervinus geminatus (Dumeril, Bibron, and

Dumeril)

Spilotespullatuspullatus (Linnaeus)

Stenorrhina degenhardtii (Berthold)

fTantilla albiceps Barbour—type-locality

*TantillaarmillataCope (T. ruficeps)

Trimetopon barbouri Dunn USNM

Xenodon rabdocephalus (Wied) (Ophis colubrinus)

ELAPIOAE

Micrurus mipartitus (Dumeril, Bibron, and Dumeril)

*Micrurus nigrocinctus nigrocinctus (Girard)

CROTALIDAE

Bothrops atrox asper (Garman)

Bothrops schlegelii (Berthold)

Species Erroneously Recorded

Some literature records that incorrectly add a species

to the fauna are considered below. Not discussed are

names known to have been wrongly applied to species

definitely occurring on the island; such names are

among those parenthesized in the list preceding.

AMPHIBIANS

Bolitoglossa schizodactyla Wake and Brame: Rand

caught one of these salamanders near the laboratory,

and the record was cited by Wake and Brame (1966)

in their original description of the species. There

seems a probability that the specimen was one captured on Cerro Campana (about 55 km SW Panama

City) several months earlier and which may have

escaped on the island. Individuals of this species

are conspicuously active on vegetation by night and

probably would not have remained undetected for

so long if naturally present on the island; the finding

of the specimen close to the laboratory buildings

makes the record doubly suspect. Myers recently

ascertained that schizodactyla is common in the

Atlantic coastal plain of Veraguas and eastern Bocas

del Toro provinces in western Panama, but there

are no acceptable records below 200 m in central

Panama where most stations are closer to 800 m.

Eleutherodactylus caryophyllaceus (Barbour) : This

distinctive little frog was listed by Dunn (1931a),

but inasmuch as it is not mentioned in his later paper

(1931b), nor reported by any subsequent worker,

it is assumed that a mistake was made. The species

is found the length of Panama, especially in wet,

subtropical forest, where it sits conspicuously on

leaves at night.

REPTILES

Anolis tropidogaster Hallowell: This species is recorded from the island under the synonymous name

A. stigmosus, by Dunn (1931a). However, it is not

present on other lists nor in the old card catalog

from which the lists were drawn (Dunn seems to

have revised the amphibian and reptile section of

the file during his visits to Barro Colorado). The
NUMBER 10

early presence of "stigmosus" on the island would

not be any more surprising than that of such opencountry inhabitants as Bufo granulosus, Anolis auratus, or Imantodes gemmistratus, but no definite confirmation seems available. Rand recently found it in

disturbed areas at Frijoles, just across the lake from

the laboratory clearing.

Ctenosaura similis (Gray): One gathers from Barbour's curious note (1932) that Ctenosaura was observed on the island, "next the quarters of Mr. James

Zetek, the resident custodian of the Barro Colorado

Island Laboratory." However, Dr. G. B. Fairchild

(verbal communication) informs us that Zetek's

residence was in Balboa, Canal Zone, not far from

the Bay of Panama. In Panama, the rock or black

iguana is confined closely to the vicinity of Pacificside beaches.

Ameiva ameiva praesignis (Baird and Girard): Dunn

(1931a) lists this species (as A. praesignis) from

Barro Colorado, but later (1940) states that it has

not been taken on the island. Allee's (1926) use of

the name A. ameiva almost certainly refers to A.

leptophrys. A. ameiva is the largest of the four

species of Panamanian ameivas and it shuns forest,

unlike the other two species {f estiva and leptophrys)

that are found in central Panama. It has long been

known to occur at Frijoles and would not be overlooked if it were on the island.

Dipsas variegata nicholsi (Dunn) : This snake was

reported by Peters (1960, pp. 138-139) on the basis

of information supplied by E. R. Dunn on two

specimens. One of these (no. 7157, a head) is in

the Barro Colorado laboratory in a jar of mixed

species labelled "not known from B.C.I." Both specimens are from the old Panamanian snake census

and, hence, probably never had specific data (other

than a general region). Furthermore, as a wildlife

preserve, Barro Colorado was not included in the

scope of the census and Dunn (1949, table 7), who

reported on the census, did not denote the species

(by asterisk) among those which he knew to occur

on the island. But it would not be surprising if D.

variegata eventually reached Barro Colorado, as it

does occur in the Chagres drainage and is not uncommon in lowland Madden Forest Preserve, about

24 km to the southeastward. It is curious that although several dipsadines occur in the region, none

has been found on Barro Colorado Island.

Extirpated Species

AMPHIBIANS

Bufo granulosus humboldti Gallardo: This toad occurs on the Pacific side of the Isthmus, mostly in

the savanna areas east and west of the Canal Zone

region of moist forest, and there are no recent reccords of it from the vicinity of Gatun Lake. The

Barro Colorado record is based solely on AMNH

22830 (Gallardo, 1965; Zetek, 1951), which was

collected by J. A. Weber on 10 August 1928.

Denrobates minutus minutus Shreve: type-locality

(Phyllobates lugubris, P. truncatus). Although

seemingly no longer on the island, this very small

frog is locally common in hill areas to either side of

the Canal Zone and occurs also in the Atlantic lowlands southwest of Colon. Specimens from Cerro

Campana (Pacific side, west of Canal Zone), the

type-locality of D. shrevei Dunn, exhibit no important differences from ones collected in the low

ridges above Puerto Pilon (Atlantic side, east of

Canal Zone), and shrevei is here considered a synonym of minutus. The dorsal light areas are golden

(sometimes tinged with orange) rather than red as

given in the type-description of shrevei.

Rana warschewitschii zeteki Barbour: type-locality.

Allee and Torvik (1927) indicate this forest frog as

being common in 1924, and Dunn (1931b) says that

it was "not rare" when he worked on the island in

1928-1930.

REPTILES

Anolis auratus Daudin: This is a grassland lizard

that apparently was eliminated on the island by

vegetational succession. However, since it was purposely re-introduced to the laboratory clearing in

1966, it is retained in the preceding list.

Gonatodes albogularis fuscus (Hallowell) : We

agree with Heatwole and Sexton (1966, p. 59) that

successional changes in the forest probably caused

the disappearance of this diurnal gecko. Gonatodes

is not commonly found in dense forest in the Canal

Zone region, where it occurs mostly about human

habitations and in opened, disturbed forest. Like

Anolis auratus, it was experimentally re-introduced

to the laboratory clearing in 1966, and, for that

reason, is retained in the checklist.
SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

There probably are a few other species that have

been extirpated from the fauna, but the above are the

only ones of which we are reasonably certain at this

time. Some additional possibilities include the frog

Smilisca phaeota, the turtles Geoemyda funerea and

Chelydra acutirostris, the stream-side lizard Anolis

lionotus, and the snakes Tantilla albiceps and Imantodes gemmistratus, none of which has been seen on

the island in recent years.

General Considerations

The faunal composition of Barro Colorado is not

static. The trend is towards an ecologically more uniform herpetofauna. The extinction or rarity of savanna

and open forest species (Bufo granulosus, Anolis

auratus, Gonatodes albogularis, Imantodes gemmistratus) doubtlessly is correlated with the decreasing

variety of habitats, as the old clearings change slowly

toward mature forest.1 Although the frog Smilisca

phaeota has a lowland forest distribution (Duellman

and Trueb, 1966, p. 313), possibly it does not find its

optimal conditions within uniformly heavy forest. Of

33 museum specimens listed from Barro Colorado by

Duellman and Trueb, 27 were collected in 1924-1928,

five in 1939-1940, and one in 1954; we have been

unable to find this usually conspicuous Panamanian

frog on the bland (except for three males released near

the laboratory by a visitor). The tiny Dendrobates

minutus is a forest frog that is most common at slightly

higher elevations; perhaps it was never more than a

fringe population at Barro Colorado, supported by repeated immigration before the lake was formed. The

same may be true of Rana warschewitschii, although

the extirpation of this species might have been due to

the arrival of a competitor (R. palmipes, see below).

Geoemyda funerea (and perhaps Chelydra as well)

1

 Enders (1939) describes early changes in levels of mammal populations. He attributes to poaching a decrease in large

herbivores and carnivores, with a corresponding increase in

other, smaller species, including paca and agouti (which,

however, are favorite foods of humans and easily hunted or

trapped). Poaching probably is not the only factor, as it seems

certain that vegetational succession must affect the mammals

as well as the herpetofauna. Relative inaccessibility of protein

in forest with decreasing edge (Dasmann, 1964, pp. 65-66,

69) might be especially effective in limiting the larger terrestrial herbivores and, consequently, their predators. Also,

although range-size requirements are poorly known for tropical mammals, it seems possible that a lack of space eventually

was a contributing factor in some case*.

probably was only a refugee from lowland swamps and

sluggish rivers and seems not to have colonized the island—at least not with much success—as have other

semiaquatic reptiles {Crocodylus, Pseudemys) that

now are intimately associated with the lake margin but

which presumably came from the Chagres River, originally a mile away.2

Of eight species added to Zetek's 1951 list (six

snakes and two frogs, see page 8), the snakes Liotyphlops and Pseudoboa are probably remnants of the

Pacific-side faunal influence that is disappearing as the

forest matures. Of the remaining six species, a few

snakes (especially Corallus annulatus and Drymarchon corais) may be recent arrivals, but only a frog

(Rana palmipes) is assuredly too conspicuous to have

been overlooked during all the early years of faunal

exploration. Rana palmipes is a lowland forest species

and has been on the island at least since 1957, but we

do not know whether its arrival coincided with the

local extinction of R. warschewitschii. Certainly these

two frogs are not precise ecological replacements, but

both include forest streams among the habitats utilized.

The list now totals 100 species, excluding ones erroneously recorded or no longer found on the island.

Although Barro Colorado is a young island and close

to the mainland, there is a real insular effect on the

fauna. During the course of vegetation change and because of the water barrier, it seems easier for a resident

population to become extinct than for new colonization to occur. This is especially evident in an ecological

assemblage of lizards that live in disturbed areas about

Gatun Lake and colonize clearings, and which probably occurred on what is now Barro Colorado Island

during the 1890s when the forest was disturbed and

extensively cut during the French attempt at building

a canal. Without a water barrier it is probable that

Gonatodes albogularis, Ameiva ameiva, Anolis auratus,

Anolis tropidogaster, and Gymnophthalmus speciosus

would have recolonized the laboratory clearing. Anolis

auratus and Gonatodes albogularis are definitely known

to have occurred on the island and have been purposely

reintroduced. Mabuya is the only member of this group

that has maintained a population in the clearing,

possibly because it is adapted also to maintain low

population levels in forest. Although some species of

amphibians and reptiles presently on the list have

"Several other successful reptiles (Kinosternon, Caiman,

Basiliscus) utilize streams as well as the lake margin, and may

have occurred here even before the Chagres was dammed.
NUMBER 10

probably disappeared from the fauna, it is conceivable

that a few additional species still remain to be found.

And a number of forest species of the region might

eventually reach the island under their own powers, as

the adjacent mainland is only 400 yards away at the

closest point; examples are Corallus hortulanus, Clelia

clelia, and Lachesis muta (bushmaster), to name a

few presumably strong swimmers known to occur in

the Chagres drainage. Whatever extinctions or colonizations might come to light in the near future, we

suggest that the actual tally of 100 species is also a

reasonable estimate of the present herpetofauna of

Barro Colorado Island and probably accurate to less

than 10 percent error one way or the other.

Based on general observation in a variety of habitats,

and also on frog vocalizations, about a third of the species in this fauna are common (starred in the list), in

the sense that they are seen or heard not infrequently,

and about a tenth of the species are actually abundant.

This might seem to differ from an observation by Heatwole and Sexton (1966, p. 54) that, "Of the 15 species

of reptiles and amphibians captured in fenced quadrats

at Barro Colorado, all were rare (represented by a

total of only one or two individuals from the 8 plots),

except for one species, Anolis limifrons." But the difference is only one of approach. Heatwole and Sexton

were studying a restricted habitat, in the region of the

forest floor, and basing their concept of abundance on

a lizard having (at that time) an extremely high population density. They were not considering arboreal species, lake margin, creek or ravine species. This, incidentally, is the reason they did not see Colostethus

nubicola (op. cit, pp. 58-59), a common little frog

along some streams in wooded ravines.

We are less certain about estimating the number of

actually rare species. The few species marked by daggers in the list are mostly those that would be conspicuous if they were present in numbers. Some species must

be very rare or at least highly localized in this region,

as for example Tantilla albiceps, which is known to

science only from the holotype that was caught on

Barro Colorado in 1925. Possibly it would take a major

portion of one's lifetime to collect all the species in a

herpetofauna of a moist, tropical lowland, even on

such a limited area as Barro Colorado Island. But as a

matter of interest to anyone concerned with the sampling of faunal assemblages, one can make a reasonable

sampling in a few weeks by utilizing varied but standard collecting techniques. This claim is justified by the

following examples of collecting success on Barro Colorado, using the estimate of 100 species as a standard.

During the wet season in July 1962, Richard G.

Zweifel sampled 32 percent of the species in 36 hours

of actual collecting. William E. Duellman and the

senior author got 43 percent of the species in 91 manhours in June 1963. As might be expected, collecting

in the dry season is not so productive: William E.

Duellman and Charles J. Cole took 27 percent of the

species in 54 man-hours in January 1964; the Nettings

obtained 39 percent of the species (22 of frogs, 17 of

reptiles) in 26 days in March 1934 (Netting, 1936).

Pertinent facts concerning these collections (except

Netting's) are set down in Table 1 and Figure 1.

MAN-HOURS COLLECTING

FIGURE 1.—Collecting success versus effort on Barro Colorado

Island. Percent of species is equivalent to number of species

since N=100 (i.e. the number estimated as occuring on the

island at present).

The wet season curve is based on data supplied by R. G.

Zweifel for July 1962 (triangles), with an extension to a

single point (square) signifying the effort of W. E. Duellman

and C. W. Myers in June 1963. Dry season data (circles) are

from W. E. Duellman and C. J. Cole, January 1964.

In some years more effort probably would have to be

expended to obtain results comparable to those mentioned above. Populations of some common forest species on the island have declined since 1964, possibly

due to the combined effects of more arid than normal

dry seasons in 1964 (2.98 inches of rainfall below average) and 1965 (3.88 inches below average). These figures are for the January-April periods, but that the

dry seasons were also prolonged is shown by December

rainfall deficiencies in excess of 7 inches for both 1963

and 1964 (December average is 10.52 inches in 41

years of record). Such climatic fluctuations appear to

influence animal populations (and hence collecting

success) in the tropics just as in higher latitudes.

Anolis limifrons underwent a particularly noticeable
8 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

TABL E 1.—Comparisons of the total herpetofauna of Barro

Colorado Island with the number of species collected within

given time limits

Group

Caccilians

Salamanders

Frogs and Toads

Turtles

Crocodilians

Lizards

Snakes

Totals:

Amphibians

Reptiles

Grand Totals

Man-Hours of

Collecting

Number

species

occurring

1

2

29

5

2

22

39

33

67

100

-

Number species collected*

A

0

0

15

0

1

9

7

15

17

32

36

B

0

0

17

2

1

12

11

17

26

43

91

C

0

0

10

2

0

9

6

10

17

27

54

•Collections: A=R. G. Zweifel, 9-21 July 1962 (wet season);

B=W. E. Duellman and C. W. Myers, 1-9 June 1963 (57

hours day, 34 hours night, wet season); C=W. E. Duellman

and C. J. Cole, 12-18 January 1964 (36 hours day, 18 hours

night, dry season).

population decline in 1964-1966, which is documented

in part by Sexton (1967).

With respect to faunal sampling, it also is instructive to plot the number of species as they have been

collected within the last five decades (Figure 2). For

this purpose we arbitrarily choose 1920 as a starting

date for collecting on the island, which was formed

about 1914 and was made a wildlife preserve and research station in 1923. A glance at Figure 2 shows that

83 of the 103 recorded species were obtained by the

end of the first decade. All the salamanders and caecilian (3 species), crocodilians (2), and virtually all

of the anurans (28 of 32), turtles (4 of 5), and lizards

(21 of 22) had been obtained. Two frogs {Eleutherodactylus cruentus, E. gaigeae), one lizard (Anolis

pentaprion), and one turtle (Geoemyda funerea) were

added in the second decade, and two additional frogs

(Phrynohyas venulosa, Rana palmipes) were obtained

between 1952 and 1957. Eight snakes

 3 were added in

the second decade and six others * within the last two

3

 Enulius flavitorques, Imantodes gemmistratus, Leimadophis epinephalus, Leptodeira (probably septentrionalis),

Oxyrhopus petoia, Pliocercus euryzonus, Siphlophis cervinus,

and Micrurus mipartitus.

4

 Liotyphlops albirostris, Corallus annulatus, Drymarchon

corcis, Ninia maculate, Pseudoboa neuwiedii, and Tnmetopon

barbouri.

decades. (No species of any group was added during

the 1940s, for obvious reasons.) Thus, only 20 species

have been added to the known fauna since the first

decade of collecting (circa 1920-1930) of which 70

percent has been snakes.5

There probably has been as much or more work on

the island since 1951 as in the early years, but only

eight species have been recently added and at least

some of these are new elements in the fauna. These

data speak well of the energy of the early collectors,

1920 1930 1940 1950

YEARS OF COLLECTING

FIGURE 2.—Cumulative totals of species of amphibians and

reptiles collected on Barro Colorado Island. Sources: Dunn

(1931a), excluding four names erroneously listed (Eleutherodactylus caryophyllaceus, Phyllomedusa dacnicolor, Ameiva

praesignis, Anolis stigmosus) but adding one (Bufo granulosus, collected in 1928); Zetek (1940), less one species of

amphibian (probably P. dacnicolor, based on a misidentification by Dunn, 1931a); Zetek (1951); present list (including

extirpated species).

whose intermittent efforts in the first decade were most

concentrated in the last several years of that period, as

indicated by perusal of the Barro Colorado annual reports. It seems possible that results similar to those of

the first decade could be duplicated in comparable forest by a party of several people working intensively for

a month or two in one wet season plus a week or so in

5

 Species added in the second decade were determined by

comparing Dunn's 1931a list (=end first decade) with

Zetek's 1951 list, inasmuch as the number of names in the

latter did not add to the simple counts of species given by

Zetek in 1940 (=end second decade). Bufo granulosus, collected in 1928, was not listed by Dunn (1931a, b) for the

island but is here added to his figures. The recent additions

are given in Zetek (1953) and the present list. Due consideration has been given nomenclatorial changes in these comparisons of several lists.

Species erroneously recorded by Dunn and by Zetek and

omitted from present calculations are listed in the legend

under Figure 2.
NUMBER 10

one dry season. One of us was part of a party that

obtained 85 species in 26 days (July, but unusually dry)

in evergreen seasonal forest of eastern Panama; most of

the species were collected about a lowland camp (130

m) although several came only from a higher elevation

(740 m).

As most experienced field workers will testify, and

as indicated in Table 1 and preceding discussion,

snakes form a large herpetofaunal segment that is difficult to adequately sample. Snakes, especially those attaining lengths in excess of 30 cm, are mostly predators

of vertebrates and this position in the food web results

in their having lower population densities than most

amphibians and other reptiles, which generally prey

on the abundant invertebrate life and even, in some

cases, on vegetation. Snakes also are behaviorally and

structurally well adapted to avoid discovery, especially

in lush tropical vegetation and in the dimness of tropical forests. However, the relative scarcity of snakes is

especially noticeable in lowland tropical regions, where

many species occur, and is the result of still additional

factors. There is a widespread belief that whereas there

are more plant and animal species in the tropics than

in higher latitudes, all of the individual tropical species

are comprised of fewer individuals. But this generalization does not pertain to the frogs and lizards, in which

there are some very abundant species, and it probably

is not true of many other groups. It does hold for tree

species in regions of rain forest, although there are notable exceptions (as in some swamp forests). Extensive

field work leads us to suspect that the generalization

is likewise valid for snakes; snake species of comparable size seem more likely to have lower biomasses in

wet (and dry?) tropical regions than in temperate

ones. Unfortunately, the quantitative data needed to

test this statement are not available. In any case, there

certainly is a latitudinal shift in the habits of snakes

that either (a) superimposes apparent scarcity on the

real rarity of individuals suggested above, or (b) causes

only the illusion of rarity. The most obvious point in

this connection is the development in wet tropical forests of a highly arboreal snake fauna. Even fairly large

species that forage on the ground are apt to be arboreal

when not active, or to spend part of their time foraging

above ground. Many species are completely arboreal.

The small and strictly terrestrial snakes are more difficult to find than their extratropical counterparts. More

are fossorial for one thing, and those that live on the

surface are most likely to be inhabitants of ground litter, where they are hard to detect even when they are

actively foraging. The rock and rotting log microhabitats, so well occupied by amphibians and reptiles in

temperate regions, are comparatively devoid of vertebrates in lowland Panama, where the space is taken

over by several kinds of quite large spiders, scorpions,

and other arachnids. Aggregations of snakes, seasonal

or otherwise, are decidedly uncommon. It would be no

great surprise to find a dozen snakes under one rock in

Kansas or in a single pine log in Florida, but in several

years of collecting in Panama, neither of us has caught

more than twelve snakes in any 24-hour period spent in

lowland forest. In Panama, at least, the semiaquatic

niche filled by Natrix in the United States is unoccupied, at least by a reptile, although there are a few

small, bottom-feeding "mud snakes"; but whether the

absence of Nat rue-like snakes has an ecological-evolutionary basis, or a primarily zoogeographic one, we are

not prepared to say.

There are 39 species of snakes in the present list and

it seems significant that Leston and Hughes (1968)

consider 40 species as "probably the upper limit for a

forest locality." These authors base their conclusion

on the census of 3.5 square kilometers of a disturbed,

semideciduous forest situation in tropical West Africa;

the climatic pattern is similar to, but drier than, that

on Barro Colorado. The present paper had gone to

press when the Leston and Hughes publication appeared, so detailed comparison of our results must wait

until later. It will be exceedingly interesting when comparable censuses become available for some small plots

of lowland tropical rain forest, which is characterized

by lack of a dry season but which has a vegetational

physiognomy much like the forest of Barro Colorado.

Acknowledgments

Present-day investigators on Barro Colorado owe

particular gratitude to those earlier workers who outlined the extent of the fauna and provided the taxonomic basis for further study. In herpetology, Emmett

Reid Dunn and James Zetek (a general biologist) deserve special mention.

We are grateful to William E. Duellman, Neal G.

Smith, Owen J. Sexton, and Richard G. Zweifel for

reading an early draft of the manuscript, and to Graham B. Fairchild and Edward Moll for certain information. Drs. Duellman and Zweifel very kindly permitted us to publish their data on collecting effort.
10 SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY

This paper was prepared while the senior author

was on the staff of the University of Kansas Museum

of Natural History, Lawrence, and a visiting scientist

(1964-1967) at the Gorgas Memorial Laboratory,

Panama City, Republic of Panama. The work was supported in part by grant GM 12020 from the National

Institutes of Health to the University of Kansas, W. E.

Duellman and G. W. Myers co-investigators.

References

Allec, W. C.

1926. Distribution of Animals in a Tropical Rain-Forest

with Relation to Environmental Factors. Ecology,

7(4) :445-468.

Alice, W. C, and Magnhild Torvik

1927. Factors Affecting Animal Distribution in a Small

Stream of the Panama Rain-Forest in the Dry Season.

Journal of Ecology, 15(1) :66-71.

[Barbour, Thomas]

1925. First Annual Report of the Barro Colorado Island Biological

Station in the Panama Canal Zone. 14 pages, mimeographed (unsigned). National Research Council.

Barbour Thomas

1932. About Iguanas. Copeia, 1932(2) :97.

Bennett, Charles F., Jr.

1963. A Phytophysiognomic Reconnaissance of Barro

Colorado Island, Canal Zone. Smithsonian Miscellaneous Collections, 145(7): 1-8, foldout map.

Brattstrom, Bayard H.

1960. Thermoregulation in Tropical Amphibians (abstract).

Tear Book of the American Philosophical Society,

1960, pages 284-287. [Anolis pentaprion and Eleutherodactylus palmatus are recorded from B.C.I. for the "first

time," with voucher specimens deposited in the

American Museum of Natural History. The specimens of the former are A. limifrons, but in any case

pentaprion does occur on the island and was listed by

Zetek. Specimens called E. palmatus are E. fitzingeri.]

Dasmann, Raymond F.

1964. Wildlife Biology, viii + 231 pages. New York: John

Wiley and Sons, Inc.

Duellman, William E., and Linda Trueb

1966. Neotropical Hylid Frogs, Genus Smilisca. University

of Kansas Publications, Museum of Natural History,

17(7):281-375.

Dunn, Emmett Reid

1931a. Preliminary List of the Reptiles and Amphibians of

the Canal Zone and the Provinces of Panama and

Colon, R.P. Pages 15-18 in Barbour, Thomas,

Seventh Annual Report of Barro Colorado Island Biological

Laboratory, Panama Canal Zone. National Research

Council, 24 pp., mimeographed. [Species known

from Barro Colorado arc so indicated, this being the

earliest of several lists of the herpctofauna. The list

contains apparently the first New World record of

Lepidodactylus lugubris, an introduced gecko, but no

definite localities are given.]

1931b. The Amphibians of Barro Colorado Island. Occasional Papers of the Boston Society of Natural History, 5:

403-421. [Includes species known at that time from

other parts of the Canal Zone and the provinces of

Panama and Col6n.]

1940. New and Noteworthy Herpetological Material from

Panama. Proceedings of the Academy of Natural Sciences

of Philadelphia, 92:105-122, plate 2.

1949. Relative Abundance of Some Panamanian Snakes.

Ecology, 30(l):39-57. [This is the most important of

Dunn's many Panamanian papers. Species known

from Barro Colorado are indicated by asterisks in

Table vn.]

Enders, Robert K.

1939. Changes Observed in the Mammal Fauna of Barro

Colorado Island, 1929-1937. Ecology, 20(l):104-106.

Evans, Howard E.

1947. Notes on Panamanian Reptiles and Amphibians.

Copeia, 1947(3): 166-170.

Gallardo, Jose M.

1965. The Species Bufo granulosus Spix (Salientia: Bufonidae) and its Geographic Variation. Bulletin of the

Museum of Comparative J£oology, Harvard, 134(4):

107-138.

Heatwole, Harold, and Owen J. Sexton

1966. Herpetofaunal Comparisons Between Two Climatic

Zones in Panama. American Midland Naturalist, 75(1):

45-60. [Especially pertinent is the conclusion that

some common tropical species have absolute population densities comparable to common temperate

forms. On Barro Colorado, Anolis limifrons had an

estimated mean density of 474 individuals per acre.]

Hilton, William A.

1946. Salamanders from Barro Colorado Island, Canal

Zone. Journal of Entomology and Z°°loSy, 38(3) :37-39.

[Salamanders generally are regarded as rare on the

island, but this paper indicates that they can be

found by special search in the dry season.]

Kenoyer, Leslie A.

1929. General and Successional Ecology of the Lower

Tropical Rain-Forest at Barro Colorado Island,

Panama. Ecology, 10(2):201-222.

Leston, Dennis, and Barry Hughes

1968. The Snakes of Tafo, a Forest Cocoa-Farm Locality

in Ghana. Bulletin de I'Institut Fondamental d'Afrique

Noire, Serie A, Sciences Naturelles, Dakar, 30(2):

737-770.

Netting, M. Graham

1936. Notes on a Collection of Reptiles from Barro Colorado

Island, Panama Canal Zone. Annals of the Carnegie

Museum, 25:113-120, plate xrv.

Ortleb, Edward, and Harold Heatwole

1965. Comments on Some Panamanian Lizards with a Key

to the Species from Barro Colorado Island, C.Z. and

Vicinity. Caribbean Journal of Science, 5(3-4): 141-

147, "September-December 1965" [= 1 November

1966]. [Anyone using this poorly constructed key

will need to translate the word "digit" as phalanx,

in both text and figure.]
NUMBER 10 11

Peters, James A.

1960. The Snakes of the Subfamily Dipsadinae. Miscellaneous Publications of the Museum of Zoology, University of Michigan, 114:1-224, plates I-VIII.

Sexton, Owen J.

1967. Population Changes in a Tropical Lizard Anolis

limifrons on Barro Colorado Island, Panama Canal

Zone. Copeia, 1967(1) :219-222.

Sexton, Owen J., and Harold Heatwole

1965. Life History Notes on Some Panamanian Snakes.

Caribbean Journal of Science, 5 (l-2):39-43.

Wake, David B., and Arden H. Bramc, Jr.

1966. A New Species of Lungless Salamander (Genus

Bolitoglossa) from Panama. Fieldiana, Zoology, Field

Museum of Natural History, 51(1): 1-10.

Woodring, W. P.

1958. Geology of Barro Colorado Island, Canal Zone.

Smithsonian Miscellaneous Collections, 135(3) :iv+39,

2 plates.

Zetek, James

1940. [Number of Genera and Species of Amphibians and

Reptiles on Barro Colorado], p. 17 in Anonymous,

Sixteenth Annual Report of Barro Colorado Island Biological Laboratory, Panama Canal Zonet National

Research Council, 43 pages mimeographed.

1951. Report on the Canal Zone Biological Area. Annual

Report of the Smithsonian Institution for 1950, Appendix

10:133-144. [The list of amphibians and reptiles,

pp. 138-141, has been the most complete tally to

date.]

1953. Report on the Canal Zone Biological Area. Annual

Report of the Smithsonian Institution for 1952, Appendix

10:150-157. [Five additions to the 1951 list are

given on page 154. Except for Phrynohyas venulosa,

preserved specimens forming the basis of the records

were found recently on Barro Colorado and sent to

the United States National Museum.]



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