The Great Basin Naturalist 
Published by the 
^ Department of Zoology and Entomology NT^ Zeotegy *ff^ 
\^\d\s>o Brigham Young University, Provo, Utah ( 0£C 15 194] 
i<a«AKt 
\oLrMK II NOVEMBER 29, 1941 
SOME OBSERVATIONS ON AMPHIBIA AT AND NEAR 
LAS VEGAS. NEW MEXICO 
ARTHUR N. BRAGG (1) 
The summer of 1940 (June 6 to August 25) afforded opportunity 
for the study of amphibians and reptiles in and about Las Vegas, San 
Miguel County, New Mexico. Field trips were taken ahiiost dail\ : 
pools, ponds, and streams investigated at every opportunity, for the 
presence of tadpoles ; and several breeding congresses of Amphibia 
observed. Representative collections of the herpetological fauna were 
made, tadpoles of several species of Anura were reared and studied 
in the laboratory, and copeous notes taken concerning ecological rela- 
tions and habitats. Specimens have been deposited in the L^niversity 
of Oklahoma Museum of Zoolog}'. 
Las Vegas is located in the A^alley of Gallinas Creek, a tributary 
of the Pecos River, in the short-grass plains. To the north and west, 
however, the elevation increases rapidly to the Aspen Zone of the 
Sangre de Christo Mountains within twenty miles up the Gallinas 
Valley. The elevation at Las Vegas is approximately 6,400 feet; at 
the edge of the Transition Zone, seven miles northwest of the city. 
it is 6,767 feet ; and the Aspen Zone occurs at about 8,000 feet. The 
greater part of the rainfall occurs in July and August (mean over a 
period of seventy years, just over three inches for each of these 
months). From late June on through the summer, afternoon and 
evening showers are frequent, a circumstance which makes the dry 
hills and mesas of the region suitable habitats for some of the noc- 
turnal . terrestrial Amphibia. Mean temperatures for June, July, and 
August are given by the U. S. Weather Bureau as 68.6. 67.1, and 
60.7° F.. respectively. It is a region of warm days and cool nights 
during the summer. 
(1) Contrilnitinn from the Department of Zoology, University of Oklahoma, 
No. 231. 
109 
The Great Basin Naturalist 
110 ARTHUR N. BRAGG \'o]. 2. X< ). .\ 
Possible breeding sites for Amphibia in this region include (1) 
permanent streams (principally the Gallinas and its tributary, the 
Arrovo de Pecos, the former passing through the center of the city, 
the latter skirting Las Vegas on the East) ; (2 ) irrigation ditches, of 
which one large one and many small ones occur; (3) ponds, formed 
b\- dams across streams, holding water for irrigation; (4) cattle-tanks 
in short-grass pastures; (5) temporary pools and ditches; (6) seepage 
l^ools from irrigation ditches, especially on the sides of mesas; (7) 
ponds and pools formed in shallow sandstone quarries on the hillsides 
just south of Romeroville, some seven miles south of Las Vegas; (8) 
beaver ponds in the Aspen Zone of the mountains, especially in the 
upper reaches of the Gallinas \''alley ; and (9) Alpine pools, formed 
by showers and melting snow\ in the higher altitudes to the north. 
In most of these, the water is muddy with suspensions of a gray clay, 
some of which appears to be in a colloidal condition. In the beaver 
ponds, in very few of the temporary pools, and in seepage pools, the 
water may be temporarily or permanently clear. In the Alpine pools 
and beaver ponds, the water is always clear. In the lower reaches of 
the streams and in the pools formed by them here, turbidity depends 
essentially upon the violence of the local or mountain rains, since after 
heavy rainfall the runofif from the steep, sparsely vegetated slopes is 
very fast. 
AMPHIBIA OBSERVED 
(1) Ambystoma tigrinum mavortium (Bairtl). One adult was 
collected from wet pavement adjacent to a muddy temporary pond, 
one mile north of Las Vegas at night in June ; another was taken in 
the basement of a house in Las \^egas in Juh'. Larvae were numer- 
ous in muddy temporary pools of large extent in and near Las \'egas 
in June and July and in clear quarry-pools most of the summer. They 
were also found in numbers in alpine pools near the snow-line at 
about 11,000 feet elevation near the Taos County line, some fort\' 
miles north of Las Vegas. Those in the quarry-pools were of vari- 
ous sizes but those in the temporary and alpine pools were small and 
individuals varied Init little in length. It seems probable that some 
specimens in this region are paedogenic, but the collection of adults 
proves that others are not. 
(2) Bufo woodhousii woodhousii (GirardL The Rocky Moun- 
tain toad is almost certainly the only Bufo in the region. At least. 
under conditions of moisture and temperature known to be the most 
favorable for other species in Oklahoma (Bragg, 1940. 1940a. 1940b) 
none were found even with thorough search. Neither were tadpoles 
• Nov. 29. 1941 AMPHIBIA AT LAS VEGAS, NEW MEXICO 1 1 1 
of other species present at any time during the summer in any of the 
waters of the region. 
B. zv. zuoodhoiisii is very abundant all about Las Vegas. They 
were especially prevalent in the valley of the Gallinas at 6,767 feet 
elevation and below and in the valley of the Arroyo de Pecos within 
the city limits ; but they also occurred high on the short-grass mesas 
and on the wooded mountain sides both at Montezuma and in Taos 
County to the north. Considering their prevalence in such situations 
in Oklahoma (Bragg, 1940a), it is interesting that none were ever 
found under street-lights at Las Vegas although actively searched for 
at several times, when they were known to be out. Since there was 
a relative scarcity of insects frequenting lights here as compared with 
Oklahoma, it seems proabbly that whenever these toads are attracted 
to streetlights, it is the prevalence of food rather than the presence 
of the lights per sc which attracts them. These toads also feed abun- 
dantly among the pines on the steep hillsides at Montezuma (in the 
edge of the Transition Zone). Since few of them were found here 
before late June, but were found almost every night thereafter when 
looked for. it seems probable that the frequent afternoon showers at 
rhis season provided sutificient moisture on the otherwise dry hills. 
Tt is probably well to note that specimens were brought to me from 
Taos County and from the valley of the Rio Grande near Chimayo, 
Rio Arriba County, the latter collected by Ezequiel Sandoval, one of 
my students. 
The breeding habits in this habitat differ somewhat from those 
of the same species in Oklahoma (Bragg, 1940a). Many tadpoles 
were present in flowing streams upon my arrival in the region in 
June. They were especialh^ abundant in the Gallinas both at Las 
Vegas and at Montezuma, six miles to the northwest, as well as in 
the Arroyo de Pecos at the eastern edge of the city. In all of these 
locations they occurred only in the flatter areas of the stream beds 
where the water was flowing with a gentle current. They were not 
found in spring-fed pools on the flood plains of these streams adjacent 
to the selected breeding sites in the main streams themselves. No 
tadpoles were found at any time in the muddy cattle tanks in the 
short-grass pastures of the region, although, basing judgment upon 
knowledge of the habits of B. w. zvoodhousii in Oklahoma, these were 
the first places investigated. Late in August, several young tadpoles 
were taken from shallow, clear water, grassy quarry-pools south of 
Romeroville. Judging from the size ranges, these had come from 
three clutches of eggs laid at different times, two of them in one pool. 
The Great Basin Naturalist 
112 ARTHUR N. BRAGG Vol. 2, Xo. 3, 
tlic other in an adjacenl pool. ( )tht.T llian the frequent light showers, 
tliere had been no rain since Aui,rust 6. and the tadpoles were too 
small to have been produced on or near this date. iMales were heard 
callini,^ all alonj^ irriijatif)n ditches as well as in the Gallinas (lurin,t; 
several nii^hts in fune wlien tliere liad been no signihcant rain. ( )n 
the other hand, none were seen or hard about suitable breeding sites 
after an 0.80 inch rain on July 12 or after heavy rain on August 5 
and (\ both of which brought (jut Scaphiopus in large numbers (see 
beyond). />'. w. ivoodhousii was never found lireeding. nor any evi- 
dence of its having bred, in roadside ditches in this region. 
These observations confirm two conclusions drawn from a stud} 
of tliese toads in Oklahoma (IJragg, 1940a) : ( 1 ) that tlie}- l)reed more 
or less independently of rain and (2) that this is a very adjustable and 
versatile species whose habits are not so fixed that they cannot l)e 
changed considerably in adaptation to various habitats. 
(3) Pseudacris triseriata Wied. This little hylid was found on 
one night only, l)reeding in considerable numbers in grassy, clear- 
water, shallow pools after the rain of 2.04 inches on .August 5 and 6. 
Many males, a few females, and one clasping pair were taken in 
one place on the north edge of the cit}'. a very few from the edge 
of another Hooded area nearl)y ; and (jne calling male from an overtiow 
of a ditch four miles to the south. The clasping pair produced a few 
eggs in the laboratory but these did not develop. Thorough sampling 
of these pools with a dipnet at two diliferent times later failed to reveal 
tadpoles. It seems probable that, of the many presumal)!}- produced, 
most fell prey to the predaceous larvae of Scapliiopus honibifrons which 
were very numerous in the pools. 
(4) Scaphiopus hammondii Baird. T wish to emphasize that 
the western spadefoot occurs abundantly about Las Vegas. It is not 
limited to California and areas immediately adjacent as implied by 
Stejneger and Barbour (1939). It bred twice during the summer, 
first during the evening of July 12 after a downpour of 0.80 inch 
in one-half hour late in the afternoon and again, on the night of 
August 6, after just over two inches of rain. Both times, many eggs 
were laid and tadpoles develo]:)ed in many pools, every one of them 
muddy and temporary in nature. 
The voice of this species has been adeciuately described by Orten- 
burger (1924) as like the loud purr of a cat but with the metallic sound 
of grinding gears. It is (|uite different from that of the closely related 
.V. honibifrons and an\- experienced person upon hearing the two species 
calling together could not possibly mistake the one for the other. The 
Nov. 29, 1941 AMPiiiruA at las vegas, nkw mkxico 1 1.^^ 
reactions ol tho males in sccuriiii^ males also (litter from those of -S". 
hoinbifroiis. According' to Trowbridj^e and Trowhridj^e, 19.v, I and 
often confirmed by my own observations), the male of the latter species 
calls with little moving" about, apparently depending upon the call to 
attract the female. In contrast, the male of S. Iiaiiuiiondii swims ac- 
tively while calling (cf. Ortenburger, 1924) and investigates any other 
spadefoot that comes near. Ten different times 1 watched two males 
swim actively toward each other, meet head on and struggle for the 
clasping position. In each case, when one has been successful, the other 
uttered its breeding cry within a few seconds. \vhereu])on it was re- 
leased immediately, ."^ince none were released before uttering the call, 
it seems probable that voice plays a part in sex-recognition in this spe 
cies. I was not successful in seeing a mating between a female and 
male. 
These differences in the calls and in the mating behavior confirm the 
results of Smith (1934) and of Tanner (1939) who concluded, ])rin- 
cipally upon diiferences in the bony structure at the top of the head, 
that S. hammondii and .S'. homhifrons are specifically distinct. The 
specific status of these two forms is further confirmed by the constant 
dift'erences in their tadpoles (Smith, 1934; Bragg, 1941). those of 
Iianinwndii having a prominent beak and notch in the jaws and over- 
developed jaw-muscles, whereas those of S. homhifrovs lack these 
structures. 
(5) Scaphiopus bombifrons (Cope). The plains spadefoot ap- 
peared in numbers, breeding in all sorts of temporary pools of both 
muddy and clear water, during and after the rains already mentioned 
in July and August. Whereas S. hmnmoudii appeared only upon the 
nights immediately following the rains. S. bombifrons called in di- 
minishing numbers for two nights after the rain in July and f<jr three 
nights in August. Most of the eggs were laid during the first night 
in each case, however. A small chorus was also heard and individuals 
seen during the afternoon of August 6 in a deep roily ditch wherein 
eggs had been laid during the rain the night before. 
These facts do not support the common idea that .S". bnuihifrDus 
appears but once during a season to breed (cf. Trowbridge and Trow- 
bridge, 1937) ; and it adds one more to the comparatively few records 
of these spadefoots having breeding activities in the daytime. 
Breeding of both species of spadefoots was observed in many dif- 
ferent pools. Some of these contained only S. bombifrons, others had 
only or mostly 5". hammondii, and still others had about equal num- 
The Great Basin Naturalist 
114 ARTHUR N. BRAGG Vol. 2, No. 3, 
hers of each species. I could find no prc^hahle reason why this should 
be so. 
In one pool which was very extensive but exceptionally shallow 
and very muddy, Scaphiopus hombifrons bred alone I)Oth in July and 
in August (determined not only by calling males but also l)y the tad- 
poles later collected). The eggs produced here in July were not 
seen but those laid in August were produced in an exceptional manner. 
Each t^g in more than fifty masses found was on a stalk of jelly 
almost exactly like those figured by Ortenburger (1924) for the eggs 
of 5". harnmondii in Arizona, except that the egg-masses were smaller. 
There were often as few as ten or twelve eggs in one mass and seldom 
more than thirty, the masses close together near the bank and fixed 
to very low vegetation at the edge of the water. F.ach tgg was at- 
tached separately to a plant so that the stalk did not occur on the 
edge of a jelly-mass as is indicated by Wright and Wright (1933) 
that they sometimes may be. This is probably the result of the small- 
ness of the masses produced. Since other small masses of eggs of 
this species have been found which did not have stalks, both in New 
Mexico and in Oklahoma, and since no eggs observed in other pools 
have had this appearance, it seems probable that the stalked eggs 
were produced as a result of some factor or factors in the environ- 
ment rather than some property intrinsic to the organisms. I have no 
idea as to what this factor may be ; but it should be noted that this 
pool was very much more shallow (nowhere more than two to four 
inches deep) than I have ever before seen used by S. hombifrons for 
breeding. 
As was observed by Gilmore (1924) for one of them, tadpoles of 
both S. bombifrons and S. hanunondii vary much in developmental 
rates, even in the same pool. They also have an independent difference 
in average size at the same age in different pools. The variation in 
size of individuals in a single pool is more marked in 6*. Jiammondii 
but the difference in individual sizes in any two pools is more notice- 
able in S. bombifrons. Seventy-one tadpoles of the latter species from 
one pool varied between 13.0 and 39.0 mm. in total length about an 
average of 27.4 mm., whereas thirty-five of the same age from another 
pool were just entering metamorphosis at an average length of 45.6 
mm. with a range of 42 to 51 mm. Since it was noted that, in general, 
the deeper the pools, the smaller the tadpoles, a temperature factor 
may explain the differences of average sizes of tadpoles of 6". bombi- 
frons taken at the same age from different pools. This will not ex- 
plain the individual variations noted in the same pools for this species 
Nov. 29, 1941 AMPHIBIA AT LAS VKGAS, NKW MEXICO 1 1 -^ 
nor the much greater variations noted for ^. liammondii, some indi- 
viduals of which have a developmental rate so fast, when compared 
with that of their sisters of the same age and in the same pool, as to 
be truly remarkable. 
In most pools observed carefully, the numbers of tadpoles of .V. 
hammondii (but not of S. bombifrons) were comparatively fewer 
than expected on the bases of calling males previously noted and of 
eggs seen. Because of this and also because tadpoles of .V. Jiammondii 
are known to be cannibalistic, I am inclined to interpret the individual 
differences in developmental rates as an adaptation, some individuals 
forging ahead of their fellows in development and feeding upon them. 
1 have no direct evidence that this is the case, however, and 1 have 
no idea as to how such favored individuals might be produced. 
Twenty-one larvae of .9. bombifrons were reared through meta- 
morphosis and kept for about three weeks in a pail of moist sand to 
note their behavior, especially as regards feeding. They were fed daily 
(often several times a day) upon small insects and spiders. Their re- 
actions and food were essentially as described by Trowbridge and 
Trowbridge (1937), with the following exceptions and additions. They 
were often out in the daytime and some individuals burrowed only 
when direct sunlight fell upon them or wdien the surface of the sand 
was allowed to become dry. In the early morning, nearly all would be 
out. In late afternoon, a few of the larger individuals were always in 
evidence. In feeding, some were more aggressive than others and these 
grew at a faster rate. The following types of organisms were eaten 
at least once (some many times) : gnats, small flies, small ants of 
several species, (large ones were offered but never eaten), thrips, col- 
lembolans, leaf-hoppers, aphids, several types of small beetles, crab- 
spiders, and other small spiders. Individuals of a species of small 
black ant were once taken by each of two of the larger toads, where- 
upon the toads hopped frantically about, clawing at their mouths, and 
thereafter refused to attack this insect. These small toads gave no 
evidence of negative phototaxis but remained active and feeding under 
an electric lamp. This observation is like that of Trowbridge and 
Trowbridge (1937) and differs from the findings of Smith (1934). 
However, as the Trowbridges noted, it does not follow that the be- 
havior in captivity necessarily is the same as in nature. 
(6) Rana pipiens pipiens (Schreber). The common leopard 
frog was the only Rana found in the region. It was very abundant 
along the water-courses and around all of the larger temporary pools 
and ditches to an elevation of at least 6,800 feet; but neither it nor 
The Great IJa.siii Xaturalist 
116 " ARTHUR N. BRAr,(; Vol. 2, No. 3, 
its tadpoles occurred in and about the beaver ponds in the higher 
readies of the GalUnas Valley, nor was it found in the alpine pools 
higher in the mountains. Alost of its tadpoles were found in the per- 
manent water of the region, principally because its breeding season had 
passed before the temporary pools had formed during the present 
season. Its tadpoles were found in one shallow quarry-pool, however. 
One adult specimen and several larvae, were presented to me from 
Chimayo, Rio Arriba County, by their collector, Mr. Ezequiel Sand- 
oval. 
In view of the question as to how many species of frogs of the 
pipiens group should be recognized in North America, the following 
characteristics of this form may be of interest : This frog had already 
bred upon my arrival in June, its tadpoles metamorphosing from late 
June to mid-July. I found no real evidence of its breeding after June 
6 although one mated pair was seen on the bank of a temporary pool 
during a warm afternoon in mid-August. As contrasted with the 
common leopard frog of central Oklahoma, it did not call after the 
rains in July and August while Scaphiopus was breeding, as could 
have been expected of the Oklahoma form ; it was relatively easy to 
catch by hand in the daytime, something which is decidedly not true 
of the Oklahoma form ; and it seldom emitted a call as it plunged 
to the water when alarmed, something very characteristic of the com- 
mon frog of Oklahoma. Structurally, it is a short-headed (or at 
least not a long-headed) type, and it does not usually have the white 
spot in the center of the tympanum, a characteristic of its Oklahoma 
counterpart. 
While differences in characteristic behavior are of no help to a 
taxonomic worker w^ith a series of alcoholic specimens before him, 
these differences should be taken into account whenever possible. After 
observing the two forms in the field, I feel certain that the frog about 
Las Vegas, New Mexico is ver}- similar to, if not identical with, the 
grass-frog of New England (Rami brachycephala of the recent check- 
list) and the leopard frog of Wisconsin and different from that of 
Oklahoma which I call Raiia sphcitoccphola (Cope). 
SUMMARY 
In summary, one Bufo, one Rana, one Pseudacris, two Scaphiopus 
and one Ambystoma apparently constitute the amphibian fauna of the 
Las Vegas region. The Bufo and Rana typically breed in the spring- 
time, the Rana before the Bufo, if one may judge from this one sea- 
Nov. 29, 1941 AMPHIBIA AT LAS VECAS, NKW MEXICO 1 17 
son's observations. 11k- I'scudacris and both species of Scaphiopus 
lireed following- rains later. 
BIBLIOGRAPHY 
liragg, Arthur X., 194(). Observations on the ecolog}- and natural 
history of Anura. I. Habits, habitat, and breeding of Bufo 
cognatus Say. Amer. Nat. 74 : 322-349 and 424-438. 
, , 1940a. Observations, etc. 11. Habits, habitat and breed 
ing of Bufo zi'oodlioiisii zi'oodliousii ( Girard ) in Okla. Amer. 
Midi. Nat. 24: 306-321. 
, , 1940b. Observations, etc. 111. The Ecological distribu- 
tion of Anura in Cleveland Count}-, Oklahoma, with notes on the 
habits of several species. Amer. Midi. Nat. 24: 322-335. 
, , 1941. The Tadpoles of Scaphiopus boDibifroiis and .S'. 
hammondii. The Wasmann Collector 4 : 92-94. 
Gilmore, R. J., 1924. Notes on the Life History and Feeding Habits 
of the Spadefoot Toad of the Western Plains. Colo. College 
Publ. (Sci. Ser.) 13: 12 pp. 7 figs. 
Ortenburger, A. L, 1924. Life History Notes — Scaphiopus — the 
Spadefoot Toad. Proc. Okla. Acad. Sci. 4: 19-20. ps. 2 and 3. 
Smith, Hobart M., 1934. The Amphibians of Kansas. Amer. Midi. 
Nat. 15: 277-528. 
Stejneger, Leonard and Thomas Barbour. 1939. Checklist of North 
American Amphibians and Reptiles, ed. 4, XVI + 207 pp. 
Harvard University Press. 
Tanner, Vasco M., 1939. A Study of the genus Scaphifjpus : the 
Spadefoot Toads. Great Basin Nat. 1 : 3-20, pis. 1-3. 
Trowbridge, Albert H. and Minnie S. Trowbridge, 1937. Notes on 
the cleavage rate of Scaphiopus boinbifroiis Cope, with additional 
remarks on certain aspects of its life history. Amer. Nat. 71 : 
460-480. 
Wright, A. A. and A. H. Wright, 1933. Handbook of Frogs and 
Toads, XI + 231 pp., 82 pis. Comstock Publ. Co., Ithaca, N. Y. 
Wright. A. PL. 1929. Synopsis and Description of North American 
Tadpoles. Proc. U. S. Nat. Mus. 74 (art. 11) : 1-70, pis. 1-9.