Golden Eye

Indian Bullfrog (Hoplobatrachus tigerinus) is a very large semiaquatic frog, measuring up to 170 mm. Dorsally greenish or brown with dark spots and often a light vertebral line. Ventrally whitish. Males become yellow in the breeding season. Skin with longitudinal rows of tubercles. Hands without webbing, feet more or less fully webbed. Males with nuptial pads on first finger and paired lateral vocal sacs. This frog was photographed at Kadalkere, Moodabidri using ShivaShankar Nayak‘s Canon EF 500mm f/4 L IS USM Lens on my Canon EOS 5D mark II.

Description
The head is slightly longer than wide, in older specimens it is wider; snout pointed, projecting, canthus obtuse; loreal oblique, slightly concave; interorbital space much narrower than the upper eyelid; tympanum distinct, almost as large as the eye; fingers obtusely pointed, first longer than second; tibiotarsal articulation reaches eye or between eye and the naris; toes obtuse, with slightly swollen tips, entirely webbed, feebly emarginated; outer metatarsal tubercle separated nearly to its base; subarticular tubercles small, a dermal fold along outer border of the fifth toe, inner metatarsal tubercle small, blunt and compressed; dorsum smooth or granular, with 6-14 longitudinal broken folds, occasionally interspersed with smooth tubercles, ventrum smooth; forelimbs of breeding male are thick, first finger is swollen, with grayish-brown velvety horny layer at its base, blue vocal sacs are located on sides of the throat.

Color: Dorsum olive green, olive or gray, with dark blotches, a light yellow vertebral streak, rarely absent; a dark canthal and a lighter labial streak often present; limbs with dark bars, which may break in dark blotches; thighs posteriorly marbled with black and yellow; a fine yellow line along upper surface of thigh, another on the inner side of calf. Ventrum white, sometimes feeble pigmentation on throat (Khan and Tasnim 1987b).

The tadpole of Holobatrachus tigerinus has a cylindrical body, which does not bulge out; tail is muscular, almost as broad as body, fins are narrow, parallel, tail tip is acutely pointed. Anterior oral disc, with nonpapillated rim. Posterior labium extensible into an additional postdisc sucker. Beak strong, prebuccal half of it is strongly serrated, medially produced into a long serrated tooth, while postbuccal half is sharp, nonserrated with a median recess to receive the median tooth of the prebuccal half. The labial tooth row formula is 5(4)/5(3), teeth are biserial in arrangement (Figure 6C). A tooth is a 0.3-0.4 mm long cylindrical body, with a gradual taper toward acute tip (Khan 1991a, 1996b).

The tadpole is predominantly carnivorous and feeds primarily on sympatric tadpoles and bodies of drowned animals (Khan 1996b). It is benthic in habits, eyes and nostrils are dorsally placed. It stalks its prey, while lying at the bottom of water, darting to catch it in its powerful jaws. Melanophores are concentrated just below eyes, and along dorsolateral sides of body; tail and fins are speckled with black, tail tip heavily pigmented. Total length of the tadpole 40-43 mm, tail 23-26 mm.

Similar species:
Ptychadena mascareniensis is smaller and has more longitudinal, continuous ridges on dorsum rather than rows of tubercles.

Distribution and Habitat
Found in Bangladesh, India, Nepal, Pakistan, Sri Lanka. Has been introduced in Madagascar.

Life History, Abundance, Activity, and Special Behaviors
Hoplobatrachus tigerinus is the largest frog in the India & Pakistani plains. It hibernates by burrowing in soil during winter as well as during drought.

Breeding activity is primarily confined to monsoons. The breeding males are lemon yellow in color, hence locally called “Basanti Dadoo”, while females remain dull and drab-colored. The deep blue vocal sacs of male are prominent against the yellowish white color of the throat of the male. The call is a powerful nasal “cronk, cronk, cronk”, which sometimes sounds like “oong wang, oong wang, oong wang” repeated several times. Calling males sit close to each other in shallow water, now and then jumping over each other. Females lurch around. One falling within the range of a male is grabbed by the male in an amplectic hold, with neighbors soon jumping on the pair and trying to dislodge them which starts much fighting, pushing, and tugging. The pair somehow moves to a quieter place where large eggs (2.5-2.8 mm diameter) are laid in several groups, each egg enclosed in a double coat of jelly. Eggs are soon attached to grass blades and often sink into the water (Khan 1969, 1996b).

Hoplobatrachus tigerinus is a voracious feeder; anything that is moving is bounced upon and swallowed. If needed it uses its anterior limbs to thrust larger food into its mouth. In addition to a great variety of insects, it feeds on a variety of items: mice, shrew, young frogs, earthworms, roundworms, juvenile snakes, and small birds. Vegetable matter and several odd objects are recorded from its stomach (Khan 1973). Lizards like Uromastyx (Daniel 1975), snakes: Lycodon aulicus, Ramphotyphlops braminus, Leptotyphlops sp., and young Ptyas mucosus have also been recorded from its diet.

The frog does not stay in water for a long time; it spends most of its time hiding and feeding in surrounding vegetation. On approach of danger, it plunges into deep water, stays underwater for 2-3 minutes, then returns quietly to the marginal vegetation undetected. In clear pools of water it hides under bottom gravel.

References
Datong, Y., and Shunqing, L. (2004). Cynops cyanurus. In: IUCN 2008. 2008 IUCN Red List of Threatened Species.
Glaw, F. and Vences, M. (1994). Amphibians and Reptiles of Madagascar. M. Vences and F. Glaw Verlags GbR., Köln.
Glaw, F., and Vences, M. (2007). Field Guide to the Amphibians and Reptiles of Madagascar. Third Edition. Vences and Glaw Verlag, Köln.