..J

~

1,"iJ

Journalof Herpelology, Vol. 17, No. I, pp. 60-69, 1983Copyright 1983 Society for the Study of Amphibians and Reptiles

Ecology of Highly Venomous Snakes: the Australian GenusOxyuranus (Elapidae)

RICHARD SHINEl AND JEANETTE COY ACEVICH2

lZoology AOS, University of Sydney, N.S.W. 2006, Australia and2Queensland Museum, Brisbane, Queensland 4006, Australia

ABSTRACT. - The taipan, Oxyuranus scutellatus, is a large slender elapid of coastal tropical Aus-tralia. The small-scaled snake, O. microlepidotus, is a similar snake from the arid zone. These areamong the most highly venomous snakes in Australia, and probably in the world. We presentinformation on body sizes, sexual size dimorphism, feeding habits, reproductive cycles, fecundityand inferred growth rates, based on dissection of museum specimens and observation of captivesnakes.

Adult snakes average approximately 1.5 m SVL in both Oxyuranus species, and males and femalesattain similar body sizes. Oxyuranus species are unique among Australian elapids in feeding exclu-sively upon endothermic prey. A wide variety of marsupials and rodents is taken: especially Rattusvillosissimus and Antechinomys laniger by O. microlepidotus, and Melomys sp., Mus musculus,Perameles nasuta and Rattus spp. by O. scutellatus. The large body size, highly toxic venom and"snap and release" bite of Oxyuranus species may be adaptations to feeding on mammalian prey.Over recent decades, taipans have become more common relative to other large elapid species: wesuggest that this may be due to the introduction of the toxic cane toad (Hulo marinus) as well ashabitat modification by agriculture.

Both Oxyuranus species are oviparous, with mating and oviposition from August to December.Fecundity (7 -20 eggs), incubation period (60-80 days), and size at hatching (300-340 mm SVL) aresimilar in both species. Captive taipans show rapid growth, with sexual maturation as early as 16months of age in males, and 28 months in females. In several aspects of morphology, ecology andbehavior, O. scutellatus is strongly convergent with an African elapid, Dendroaspis polylepis (theblack mamba).

We have less ecological informationabout snakes than about any other terres-trial vertebrate group of comparable size.Venomous snakes are particularly poorly-known, and highly venomous specieshave attracted almost no serious studyfrom ecologists. However, highly ven-omous snakes are a conspicuous compo-nent of the snake fauna in many areas ofthe world (e.g., Australia, Asia, Africa).Studies of the ecology of such snakes mayhelp us to understand the evolutionarypressures for, and consequences of, thepossession of extremely toxic venoms, andepidemiological factors in snakebite. Thepresent paper provides ecological data ontwo Australian snake species which areamong the most highly venomous in theworld.

Allowing for venom toxicity and aver-age venom yield per bite, the number ofmouse LDsodoses per bite is much higher

for Oxyuranus microlepidotus (218,000)andO. scutellatus (94,000) than for any othersnakes, including sea snakes, investigatedto date (Broad, Sutherland and Coulter,1979). For example, the bite of O. micro-lepidotus contains about 50 times as manyLDso doses as does the bite of the KingCobra (Ophiophagushannah),and about 100times as many as that of the eastern dia-mondback rattlesnake (Crotalus adaman-teus) (Broad, Sutherland and Coulter, 1979).

MATERIALSAND METHODS

The two species which we studied wereformerly placed in separate genera: Oxy-uranus scutellatus and Parademansiamicro-lepidotus (e.g., Cogger, 1975). However,strong similarities between these snakesin morphology, venom, behavior andkaryotype suggest that they should beplaced together in the genus Oxyuranus(Covacevich et aI., 1981). Both are large,

TAIPAN ECOLOGY

FIG. 1. Upper photograph: Taipan, Oxyuranusscutellatus. Lower photograph: Small-scaled snake,O. microlepidotus. Photographs by A. Easton,Queensland Museum.

"

brown, slender-bodied snakes (Fig. 1), andare predominantly diurnal (Covacevich etal., 1981). The snakes differ greatly, how-ever, in geographical distribution. The tai-pan (0. scutellatus) occurs coastally in areasof relatively high rainfall. Taipans attainhigh densities in sugar-cane fields andtheir environs. In contrast, the small-scaledsnake (0. microlepidotus) is restricted toextremely arid inland regions (Fig. 2).Typical habitat for this species is "ashydowns" country which has only sparse,low vegetation.

Published information on the ecologyof Oxyuranus is scattered and largelyanecdotal. Our study summarizes thisinformation, and presents original databased on dissection of all available

museum specimens (21 O. microlepidotus,114 O. scutellatus) in the collections of theAustralian Museum, Queensland Museum

61

.°,"""",,",

.Omio,"'",,"'"'""

FIG. 2. Geographic distribution of the twoOxyuranus species. Circles show O. scutellatus, dotsshow O. microlepidotus. Lines are isohyets forannual precipitation (lOO mm and 500 mm).

(QM), National Museum of Victoria, andSouth Australian Museum, and recentfield work on Oxyuranus microlepidotus.The following data were taken frommuseum specimens: snout-vent length(SVL); sex; reproductive maturity orimmaturity (criteria were: males-largetestes or opaque efferent ducts; females-gravid, or enlarged oviducts, or ovarianfollicles >5 mm diameter); diameters ofovarian follicles or oviducal eggs; and gutcontents. In many specimens, the onlyfood items in the alimentary canal weremammalian hairs in the rectum. Thesehairs were identified using the guide byBrunner and Coman (1974), in conjunc-tion with fur samples from all of the com-mon small mammals within the geo-graphic range of the Oxyuranus species.Further data were provided by CharlesTanner, who has bred both Oxyuranusspecies in captivity, and maintained cap-tive O. scutellatus over a 20-year period.

RESULTS

Body Sizes.- Table 1 shows that femalesreach similar body sizes in both species(means of 144 cm, 145 cm SVL), but maletaipans grow much larger (mean SVL 156cm) than male small-scaled snakes (mean

62 R. SHINE AND J. COVACEVICH

TABLE1. Sample sizes, body sizes, and sexualdimorphism in body size in adult specimens oftwo Oxyuranus species. All snout-vent lengths(SVL) in cm.

SVL 132 cm). The difference in body sizebetween the sexes is close to statistical sig-nificance in O. scutellatus (N = 55, 23;median test, 1 df, X2= 3.1, .05 < P < .10)but not in O. microlepidotus (N = 13, 6;median test, 1 df, X2= 0.02). In bothOxyuranus species, males mature at muchsmaller body sizes than do females (Table1: 92 cm in 55 versus 133 cm SVL in ';?';?

for O. microlepidotus;78 cm in 00 versus. 101 cm SVL in ';?';? for O. scutellatus).

Food Habits.-Based on museum speci-mens, individuals of Oxyuranus feedexclusively on endotherms: 18 mammalsand one bird were recorded in O. scutel-latus guts, and nine mammals in O. micro-lepidotus (Table 2). The snakes take a widevariety of mammals, including both mar-supials and rodents. Many prey items arelarge (e.g., a young bandicoot, Isoodonmacrourus, of 40 gm mass). Kinghorn(1923) reports the occurrence of remainsof a quoll, Dasyurus hallucatus in the gutof a large taipan (TL 275 cm). Adult quollsattain a mass of approximately 600 gm.Feeding apparently occurs year-round inboth Oxyuranus species, but sample sizesare too low to reveal any seasonal trends.

Mode of Reproduction.-Both Oxyuranusspecies are oviparous: oviducal eggs ofboth species were seen in the course ofthe study. The stage of embryonic devel-opment at oviposition was determined foran egg laid by a captive taipan (donatedby N. Charles). This embryo (QM ]38703)was at stage 28 in the classification ofHubert and Dufaure (1968): the head was

large and birdlike and the body tightlycoiled.

Size at Hatching.-Several O. scutellatuspreserved at hatching measured between30.2 and 32.6 cm SVL. The smallest taipancollected in the field measured 31.5 cmSVL. No small specimens of O. microlep-idotus have been collected, but fifteen neo-nates hatched in captivity ranged from 37to 43 cm total body length. SVL measure-ments were not recorded, but examina-tion of young taipans shows that 40 cmtotal length corresponds to 34 cm SVL.Hence, size at birth is similar in the twoOxyuranus species. Eggs of O. microlepi-dotus averaged 6 cm X 3.5 cm (Covacevichet al., 1981).

Seasonal Reproductive Timing.-Severallarge (clearly adult) males of both Oxy-uranus species possessed small testes anddid not contain sperm in the efferentducts.

Female taipans show clear seasonalvariation in ovarian follicle diameters (Fig.3). Ovigerous females are found fromAugust to November, and post-oviposi-tion specimens with very small follicles(< 10 mm) from September to March. Fol-licles increase in diameter during the firsthalf of the year, but vitellogenesis prob-ably is concentrated close to the time ofovulation (note June specimen with smallfollicles; Fig. 3).

Data on captive taipans confirm thisseasonal schedule of reproduction. Copu-lation has been observed in August andin early December, and oviposition inOctober and February (N. Charles, pers.comm.). The interval between copulationand oviposition was 68 days in one case,and 70 days in another. Taipans in theMelbourne Zoological Gardens mated inSeptember and October, and oviposited inNovember (c Banks, pers. comm.). Fur-ther evidence for this phenology comesfrom field observations of taipans incoastal north Queensland: ovigerousfemales may be found (usually basking in"windrows" in canefields) from August toSeptember (K. Day, pers. comm.).

Sample sizes of O. microlepidotusare toolow to draw any conclusions from field

..Species

O. micro- O. scute/-Variable lepidotus latus

Sample size <3<3 13 55

Sample size 22 6 23

Mean SVL <3(SE) 132.0 (6.8) 156.4 (3.6)Mean SVL 2 (SE) 143.8 (6.3) 145.0 (4.4)Size range <3<3 92.0-169.0 78.3-226.0

Size range 22 133.0-170.0 101.4-193.0

TAlPAN ECOLOGY 63

TABLE2. Prey items identified from Oxyuranus digestive tracts.

Snake species

Oxyuranus microlepidotus

Prey speciesNumber

of records

Marsupials-Antechinomys laniger-dasyurid sp.

Rodents-Mus musculus

-Rattus sp.-R. villosissimus

Mammal-sp. unknownMarsupials-Isoodon macrourus

-Perameles nasuta

Rodents-Melomys sp.-M. burtoni

-M. cervinipes-Mus musculus-Rattus sordidus

-R. tunneyi

Bird-sp. unknown

Oxyuranus scutellatus

31212

1134115111

samples (Fig. 3). Fortunately, data areavailable on captive snakes (c. Tanner,pers. comm.). Attempted courtship hasbeen recorded in January, February,March, September, October and Decem-ber, and mating has been seen in Marchand October. Oviposition occurred twicein December, once in November and oncein March (the two latter records from thesame female, in successive years).

Incubation Periods.-One clutch from acaptive taipan hatched in late April (69days after oviposition), when incubated atroom temperature (probably 25°-30°C, N.Charles, pers. comm.). Other clutcheshatched in January, after 64 to 68 daysincubation (R. W. Dunn and C. Banks,pers. comm.). Eggs of O. microlepidotushatched in February, 66 days after laying(Covacevich et al., 1981).

Clutch Sizes.-Fecundity data for O. scu-tellatus are shown in Figure 4. Clutch sizeranged from 7 to 17 eggs, with a mean of11.4 (SEM = 1.3, N = 8). Fecundity wasindependent of maternal body size (r2 =0.23, 7 df, n.s.). Captive taipans producedclutches of 7 eggs (including one infer-tile), 15 eggs (all fertile), 10 eggs and 19eggs (N. Charles, pers. comm.; C. Banks,pers. comm.). Clutch sizes of captive O.microlepidotus were as follows: 20, 19, 12,

15 (including two infertile), and 15 (at leastten infertile). The mean of these five rec-ords is 16.2 (SEM = 1.5).

Seasonal Abundance.-Figure 5 showsthat taipans may be collected throughoutthe year, but are taken most commonly inlate winter and spring (Aug.-Oct.).

DISCUSSION

One corollary of highly toxic venom insnakes is great public interest in thesespecies. In the case of the taipan,.this pub-lic interest has stimulated several zoos toinclude taipans in their exhibits. At leastthree such zoos have successfully bred tai-pans, as have private reptile-keepers (Bar-nett, 1978; N. Charles, pers. comm.).Hence, despite the comparative scarcity ofOxyuranus in museum collections, a greatdeal is known about reproduction of O.scutellatus in captivity. The small-scaledsnake (0. microlepidotus) is less well-known; live specimens did not becomeavailable to scientists until 1975(Covacev-ich and Wombey, 1976), and few speci-mens of this species have been collected(Table 1).Our information on O. microlep-idotus reproduction is entirely due toCharles Tanner's success in breeding cap-tive specimens.

Body Sizes.-Both Oxyuranus species

64 R. SHINE AND J. COVACEVICH

40

E 30!.

>!0( 20is

d::;2 10

..f M A M J J A

MONTH

0 N

FIG. 3. Seasonal changes in diameter of thelargest ovarian follicle, or oviducal egg, in Oxy-uranus scutellatus (circles and dots) and O. micro-lepidotus (squares). For O. scutellatus, dots showovarian follicles, and circles show oviducal eggs.For O. microlepidotus, solid squares show ovarianfollicles, open squares show oviducal eggs.

rank among the largest Australian ela-pids; O. scutellatusprobably attains greaterbody sizes than does any other species.This large body size may be an adaptationto feeding on large prey (mammals; seebelow).

The ttend for sexual size dimorphismin taipans (55 average 156 cm SVL, ~~average 145 cm: Table 1) may be relatedto the occurrence of male combat in thisspecies. Combat in captive taipans hasbeen noted by Worrell (1970), and fieldobservations by Hosmer (1953) stronglysuggest male combat behavior (althoughthe sexes of the snakes involved were notdetermined). Among snakes in general,there is a strong correlation between malecombat behavior, and sexual size dimor-phism in which the male is the larger sex(Shine, 1978a). Male combat and malesuperiority in body size are commonamong large Australian elapids (e.g.,Shine, 1977a, 1978b).

Food Habits.- The specialization ofOxyuranus upon mammalian prey (Table2) is consistent with observations on cap-tive snakes (c Tanner and N. Charles,pers. comm.) and with previous reports(Kinghorn, 1923; Thomson, 1935; Carnet,1968;Warrell, 1970;Cow, 1976, 1980; Bar-nett, 1978;Stackhouse, 1978;McPhee, 1979;

1716

..15

14

TAlPANFecundityvs SVL ~

13

12

~ 11

~ 10::> 9cl

... . .

7- .D

130 140 150 160 170 180

MATERNALSNOUT-VENT LENGTH(cm)

FIG. 4. Relationship between maternal bodylength and clutch size in Oxyuranus scutellatus.

120 190

Broad et al., 1979;Covacevich et al., 1981).The suggestion that young taipans mayfeed on skinks as well as mammals(Kinghorn, 1923;Cow, 1976;Barnett, 1978)is not supported by gut contents analyses(Table 2) or by observations in captivity:young taipans are attracted to small mov-ing prey, but will not attack ectotherms(N. Charles, pers. comm.).

This specialization of Oxyuranus uponmammalian prey is unique among Aus-tralian elapid snakes. Extensive data onfood habits are available for 28 elapidspecies (Shine, 1977b, 1980a, b, and un-published data). Mammals comprise lessthan 10% of the prey items taken in allbut six of these 28 species. The six mam-mal-eating species are a diverse group:Tropidechiscarinatus (48%of prey items re-corded were mammals), Hoplocephalusste-phensi (44%), Pseudechis guttatus (39%),Acanthophis antarcticus (32%), Pseudonajatextilis (25%)and Echiopsiscuria (14%).Thevast majority of mammals taken by allthese species are introduced house mice,Mus musculus. In contrast, Oxyuranusspecies consume a wide range of mam-malian prey (Table 2). The large size ofsome prey items reflects the large bodysize of the snakes. The only Australiansnakes likely to overlap significantly indiet with Oxyuranus are the pythons.However, the marked differences in for-aging strategies between the two types ofsnakes-fast-moving, venomous, usuallydiurnal versus slow-moving, constricting,

.-

TAIPAN ECOLOGY

usually nocturnal-may well result in dif-ferences in prey types taken.

We interpret the following characteris-tics of Oxyuranus as adaptations to feedingon mammals:

(a) Large body size-enabling large preyto be eaten.

(b) High venom toxicity-enabling Oxy-uranus to feed on large prey (e.g., rats)which must be immobilized rapidly,before they can injure the snake.

(c) Immediate release of prey afterstrike-unlike other Australian ela-pids, O. scutellatus do not retain theirinitial hold on the prey until strug-gling ceases: the prey is releasedinstantly after the strike.

The "strike and release" bite of Oxy-uranus, like high venom toxicity, may bean adaptation to the retaliatory ability ofmammalian prey. Fleay (1981) describeshow a large taipan was killed by a ratwhich was held by the snake for a fewseconds after the intial strike.

Although both Oxyuranus species feedon a wide variety of mammals (Table 2),the difference in habitats occupied by O.microlepi£l6tusand O. scutellatusmeans thatthere is little overlap in the prey speciestaken. The small-scaled snake lives in aridregions of unpredictable rainfall, wheresmall mammals (especially Rattus villos-issimus) undergo massive periodic fluctua-tions in abundance (e.g., Watts and Aslin,1981). In contrast, taipans exploit rela-tively high-rainfall areas where mamma-lian densities are high and relatively con-stant (Watts and Aslin, 1981). Thisapparent difference in food supply maynot always be the case: in the first detailednotes on the taipan, Thomson (1935,p.730)describes this species as being numerous"only . . . where there exist extensive col-onies of a Rattus, apparently R. villosissi-mus, which forms its chief food source.The taipan frequents holes in the groundin the country infested by the rats." Thissituation is exactly that characteristic ofpresent-day populations of O. microlepi-dotus.

The specialization of taipans on mam-

65

10en~ 8«6i 6LI-

0 4""

~ 2~::JZ F"M"A"M"J"J'A"S"O'N"D

MONTH

FIG, 5, Seasonal abundance of taipans, Oxy-uranus scutellatus, represented in museum collec-tions.

malian prey means that these snakes havebeen little-affected by the introduction ofmarine toads, Bufo marinus, into north-eastern Australia in the 1930's. Snakesattempting to eat toads are killed by thetoads' toxins (Covacevich and Archer,1975), with the result that most large ela-pids apparently have decreased in num-bers wherever the toads have invaded,especially in cane-growing areas ofQueensland. There has been no apparentdecline in taipan numbers over the sameperiod (K. Day, pers. comm.).

This apparent shift in species compo-sition of the snake fauna after introduc-tion of Bufo is an interesting phenome-non, but a difficult one to quantify. Wehave examined Queensland Museumaccession records to determine relativenumber of different snake species regis-tered from coastal Queensland (less than200 km from the coast) over the period1911 to 1982. If the introduction of Bufomarinus has depressed densities of largefrog-eating elapids (Acanthophis antarcti-cus, Pseudechis australis, P. porphyriacus,Pseudonaja textilis), but not of Oxyuranus,then this trend should be reflected in thenumber of taipans registered relative tothe numbers of the other large elapids.The data are consistent with the predic-tion of increased relative numbers of tai-pans following the introduction of canetoads in 1935 (Fig. 6). A significant changein relative numbers of taipans registeredoccurred between the 1940'sand the 1950's(testing 1911-1940 versus 1941 to present,Mann-Whitney U test, U = 0, NI = 4,Nz = 4, P = .01). An alternative test also

66 R. SHINE AND J. COVACEVICH

1910 .20 .8040 .50

DECADE

FIG. 6. Number of taipans registered inQueensland Museum over the period 1911 topresent, as a proportion of the total number oflarge elapids registered. Data from coastalQueensland (200 km from coast) only. Arrowshows time when Bufo marinus was introduced.

.60 70.30

reveals a significant increase in relativetaipan numbers with time (taking 1911-1920 as zero, 1921-1930 as 1, etc.; r2= .78,N = 8, P < .01). However we cannot besure that this change in taipan numbersis due to Bufo marinus;agricultural clear-ing has drastically affected coastalQueensland over this period. Clearing bythe sugar industry has provided largeareas of open habitats and "windrows."This may have increased densities of rats,and hence taipans, while at the same timedisadvantaging elapid species that are de-pendent on forested areas.

Reproduction.-Data presented in thispaper are consistent with publishedreports of reproduction in captive taipans(Table 3), in respect to oviposition dates,clutch sizes, incubation periods, and sizesof eggs and hatchlings. The inference thatmating occurs from July to December(based on female reproductive cycles andobservations in captivity) is consistentwith statements by Slater (1959)and Jones(1977). Hosmer's (1953) observations ofprobable male combat in taipans occurred

in September, and Worrell (1970) notesthat combat occurs in spring.

The production of two clutches of eggswithin a single summer season is com-mon but certainly not universal in ovip-arous squamates from warm climates(Fitch, 1970). Most records of captivereproduction in Oxyuranus report only asingle clutch each year, but examples oftwo successive clutches have beenreported both in O. scutellatus(Peters, 1972;clutches in December and January) and O.microlepidotus (c Tanner, pers. comm.;clutches in November and March). Mul-tiple clutches probably are produced inmany oviparous Australian elapids dur-ing particularly favourable years (e.g.,Shine, 1977c, 1980a, b).

Growth Rates.-Observations on captivejuvenile taipans consistently reveal rapidgrowth rates. Oxyuranus scutellatus aver-age 31 cm SVL at hatching, and have beenrecorded to attain lengths of 56 cm SVLin three months (R. W. Dunn and CBanks, pers. comm.), 74 cm in 5 months(Peters, 1972), 66 cm in 8 months (Slater,1959) and over 100 cm in 12 months(Peters, 1972).The mean growth rate fromthese four records is 6.7 crp. SVL permonth.

We suspect that rapid growth is alsoattained in the field situation. Direct evi-dence is lacking, but we note that taipansare found in warm climates, with activity(Fig. 5) and feeding occurring year-round;and of 114 taipans for which data wereavailable, only nine were field-caughtsnakes less than 100 cm SVL. This scarcityof juveniles suggests that snakes in thefield, like those in captivity, grow rapidlythrough this range of small body sizes.Body-length records for the field-collectedjuveniles show two groupings: (a) snakes30 to 40 cm SVL in March-June, undoubt-edly recent hatchlings, and (b) snakes 65to 85 cm SVL in September-November.This latter group is exactly the size onewould expect from growth rates in captiv-ity (31 cm SVL at hatching, plus 6.7 cm/month for 7 months, equals 78 cm SVL inOctober). Thus, these 65 + cm SVL snakesare likely to be in their first year of life.

TOTALNUMBEROF SNAKES59 24 39 25 B8 75 184 18

.35 .

.30

'" Bolo ;o"od,,"d

Z .25£ . .0

.20 .z0 .151;::0"-

1O[.. .

.05 .

TABLE 3. Reproduction in captive taipans, Oxyuranus scutellatus.

Incubation Incubation HatchlingEgg size Egg weight temperature period total length

Oviposition date Clutch size (mm) (gm) ("C) (days) (mm) Authority

October 7 50-60 - - - - Thomson, 1933

July-Aug. 14-18 70 - 32 91-95 318-432 Slater, 1956>!

January 20 63X38 - 27 107 380 Fleay, 196010-20 <50 - - 70-98 >559 Worrell,1970 >

Nov., Dec., Jan. 13, 18, 22 70 30 27 -28 76-82 410-460 Peters, 1972ZtT1

(wt. 23-33 gm) nDecember 12,19 52-72 - - 64-69 600 Barnett, 1978 0

r'13-20 52 21-24 - 70 381 Gow, 1980 0

CJ7-20 50-62 - - 64-68 - Covacevich et aI., 1981 ><

November 10-19 60 33.2 - 64-68 445 (410-510) R. W. Dunn & CBanks,(wt. 17-23 gm) pers. comm.

Oct., Feb. 7,15 - 17-38 25-30 69 (wt. 18-26 gm) N. Charles, pers. comm.(x = 32.0,

SEM = 0.7)

68 R. SHINE AND J. COYACEVICH

This rapid growth means that sexualmaturity may be attained at a surprisinglyearly age for such a large snake. Male tai-pans mature at approximately 80 cm SVL,and females at 100 cm (Table 1). If growthrates in captivity are similar to growthrates in the wild, male taipans wouldattain maturity (first mating) at approxi-mately 16 months of age, and females ayear later (28 months). These are exactlythe ages at which males and females ofcaptive taipans have first been observedto breed (Peters, 1972;R. W. Dunn and C.Banks, pers. comm.). We infer that tai-pans, despite their large body size, attainsexual maturity at similar ages as other,smaller Australian elapids (Shine, 1978band subsequent publications). Oxyuranusscutellatus also resembles other elapids inthe trend for males to mature at smallersizes, and younger ages, than do females-even though males eventually may growto be the larger sex. This sexual bimatur-ism probably reflects different reproduc-tive "costs" in males and females (Shine,1978b).

Overview.- The two species of Oxy-uranus are similar to each other in bodysize, diet, fecundity, hatchling size, andincubation period, providing further sup-port for their inclusion in a single genus(Covacevich et at., 1981).At the same time,these two species differ strongly from theother Australian elapids in their special-ized diet. We have suggested that Oxy-uranus characteristics such as body size,venom toxicity and feeding behaviour,reflect adaptations to feeding upon mam-malian prey. Although no strong parallelswith other Australian elapids are evident,many similarities may be noted betweendata presented here on the taipan and byFitzsimmons (1962)on an African elapid-Dendroaspis polylepis, the black mamba.These two species resemble each other inbody size, general morphology, colour,venom toxicity, I~snap and release" bite(in contrast to "chewing" bites in otherelapids of both continents), clutch size (9-14 in Dendroaspis versus 7-17 in Oxy-uranus), hatchling size (40-50 cm totallength), rapid growth in juveniles, male

combat, males growing larger thanfemales, and feeding primarily on mam-mals. These similarities clearly representevolutionary convergence rather thantaxonomic affinity (Saint Girons andDetrait, 1980).

Acknowledgments.-We dedicate thispaper to Charles Tanner, a pioneer ofAustralian herpetology and the first tobreed Oxyuranus microlepidotus in captiv-ity. We thank Mr. Tanner for allowing usto use his extensive data on captive O.microlepidotus.N. Charles, R. W. Dunn, C.Banks and K. Day offered valuable rec-ords of taipan reproduction. G. Ross andL. Hall identified mammalian prey items.A. Greer and H. Cogger (AustralianMuseum), J. Coventry (National Museumof Victoria) and T. Schwaner (South Aus-tralian Museum) gave permission to dis-sect specimens in their care. This studywas supported by the Australian ResearchGrants Committee.

~

.:

I

LITERATURE CITED

BARNETT,B. 1978. Taipan. Vie. Herp. Soc. 9:16-20.

BROAD,A. J., S. K. SUTHERLAND,ANDA. R. COUL-TER. 1979. The lethality in mice of dangerousAustralian and other snake venom. Toxieon 17:661-664.

-, -, C. TANNER,AND J. COVACEVICH.1979. Electrophoretic, enzyme, and prelimi-nary toxicity studies of the venom of the small-scaled snake, Parademansia micralepidata (Ser-pentes: Elapidae), with additional data on itsdistribution. Mem. Queensland Mus. 19:319-329.

BRUNNER,H., ANDB. COMAN. 1974. The identi-fication of mammalian hair. Inkata Press, Mel-bourne. 176 pp.

COGGER,H. G. 1975. Reptiles and amphibians ofAustralia. A. H. and A. W. Reed Pty. Ltd., Syd-ney. 608 pp.

COVACEVICH,J., ANDM. ARCHER. 1975. The dis-tribution of the cane toad, Bula marinus, inAustralia and its effects on indigenous verte-brates. Mem. Queensland Mus. 17:305-310.

-, S. B. McDoWELL, C. TANNER,AND G. A.MENGDEN. 1981. The relationship of the tai-pan, Oxyuranus scutellatus, and the small-scaledsnake Oxyuranus micralepidatus. In Banks, C. B.and A. A. Martin (eds.), Proceedings of theMelbourne Herpetological Symposium 1980.Pp. 160-168. The Melbourne Zoological Board,Parkville.

-, AND J. WOMBEY. 1976. Recognition of

TAIPAN ECOLOGY

Parademansia microlepidotus (McCoy) (Elapi-dae), a dangerous Australian snake. Proc. Roy.Soc. Queensland 87:29-32.

FITCH,H. S. 1970. Reproductive cycles in lizardsand snakes. Mise. Publ. Mus. Nat. Hist. Univ.Kansas 52:1-247.

FITZSIMMONS,V. F. M. 1962. Snakes of southernAfrica. Macdonald, London. 423 pp.

FLEAY,D. 1981. Looking at animals. BoolarongPress, Brisbane. 135 pp.

GARNET,J. R. 1968. Venomous Australian ani-mals dangerous to man. Commonwealth SerumLaboratories, Parkville. 86 pp.

Gow, G. F. 1976. Snakes of Australia. Angus andRobertson, Sydney. 88 pp.

-. 1980. History of the taipan Oxyuranusscutellatus-with two new distribution rec-ords. Northern Territory Natural. 1:15-19.

HOSMER,W. 1953. An account of supposed mat-ing of the taipan, Oxyuranus scutellatus (Peters).North Queensland Natural. 22:1-3.

HUBERT,J., ANDJ. P. DUFAURE. 1968. Table dedeveloppement de la Vipere aspic: Viperaaspis.1. Bull. Soc. Zool. France 93:135-148.

JONES,P. 1977. Search for the taipan, the storyof Ram Chandra. Angus and Robertson, Syd-ney. 112 pp.

KINGHORN,J. R. 1923. A new genus of Elapinesnake from north Australia. Rec. Aust. Mus.14:42-45.

MCPHEE,D. 1979. The observer's book of snakesand lizards of Australia. Methuen of Australia,Sydney. 157 pp.

PETERS,U. 1972. Breeding of the taipan (Oxy-uranus scatellatus) in captivity. Bull. Zoo. Man-age. 4:7-9.

SAINTGIRONS,H., AND J. DETRAIT. 1980. Com-munates antigeniques des venins et systema-tique des Elapinae. Bijdr. tot. Dierkunde 50:96-104.

69

SHINE, R. 1977a. Reproduction in Australianelapid snakes. I. Testicular cycles and matingseasons. Aust. J. Zool. 25:647 -653.

-. 1977b. Habitats, diet and sympatry insnakes: a study from Australia. Can. J. Zool.55:1118-1128.

-. 1977c. Reproduction in Australian elapidsnakes. H. Female reproductive cycles. Aust. J.Zool. 25:655-666.

-. 1978a. Sexual size dimorphism and malecombat in snakes. Oecologia 33:269-278.

-. 1978b. Growth rates and sexual matu-ration in six species of Australian elapid snakes.Herpetologica 34:73-79.-. 1980a. Comparative ecology of threeAustralian snake species of the genus Cacophis(Serpentes: Elapidae). Copeia 1980:831-838.-. 1980b. Ecology of eastern Australianwhipsnakes of the genus Demansia. J. Herpe-tol. 14:381-389.

SLATER,K. 1959. Incubation of New Guinea tai-pan eggs. Aust. J. Zool. 12:306-307.

STACKHOUSE,J. 1970. Australia's venomouswildlife. Paul Hamlyn, Sydney. 144 pp.

THOMSON,D. F. 1933. Notes on Australian snakesof the genera Pseudechis and Oxyuranus. Proc.Zool. Soc. (London) 1933:855-860.

-. 1935. Preliminary notes on a collectionof snakes from Cape York Peninsula. Proc.Zool. Soc. (London) 1935:723-731.

WATTS,C. H. S., AND H. J. ASLIN. 1981. Therodents of Australia. Angus and Robertson,Sydney. 321 pp.

WORRELL,E. 1970. Reptiles of Australia. Angusand Robertson, Sydney. 207 pp.

Accepted: 22 June 1982.