CHAPTER 3

FOOD AND FEEDING HABITS

Introduction

The food of several species of anura inhabiting

temperate regions has been studied by several workers

(Noble, 1918, 1924; Cott, 1932, 1957; Smith, 1953;

Taylor, 1958; Brooks, 1959; Berry, 1970; Blackith and

Speight, 1974). However, the food and feeding habits of

only a few tropical species have been investigated

(Khera, 1975; Nigam, 1979; Battish, 1988, 1989;

Sreelatha, 1990; Mallick and Mallick, 1980, 1981).

R. tigerina plays a significant role in controlling

agricultural pests in the field (Abdullali, 1985). All

India coordinated MPEDA Project Report (1989) on the

survey of frog populations in Kerala, Maharashtra,

Gujarat, Andhra Pradesh, Orissa, West Bengal and Kar-

nataka has shown that insects and la~rvae formed the major

constituents of the food of juvenile frogs; in large

frogs, crabs and tadpoles formed tbe major constituents

of the food. The food and feeding habits of

2 1

R. hexadactyla are not fully known (Chacko and Krish-

namurthy, 1951; Mondal, 1970; Andrews, 1979). Hence, the

present study is an effort directed not only towards

collecting data on the natural diet of this frog but also

towards determining the role it plays in the economy of

nature.

Materials and Methods

The stomach content analysis of R. hexadactyla

was carried out from January 1988 to December 1989. A

total of 408 frogs (102 males and 306 females) were used

in the present study. The frogs were collected during

night and were immediately killed. They were brought to

the laboratory, their weight was recorded and the

stomachs removed and preserved in 10% formalin. For

studying the food, stomach contents were taken out in a

petridish after incising the stomach longitudinally. The

stomach and stomach contents were weighed and recorded.

The contents were examined under a binocular dissecting

microscope. Using diagnostic taxonomic characters, the

food contents were identified.

2 2

Resul ts

The monthly distribution of stomach contents

expressed as percentage of total body weight with respect

to sex and month is shown in Table 3. The male frogs were

found to consume more food than ftemales except in the

month of May, June and September. Table 4 represents the

classified food item of R. hexadactyla and its monthwise

distribution. It has been found that this frog's primary

food was insects, but other animals like spiders, crabs,

centipedes, millipedes, earthworms and molluscs were also

eaten. The consumption of insect per frog (Table 4 ) was

high in the month of March, May, June, July and August.

The frog fed on a variety of animals belonging to 20

orders.The most predominant insect orders were Orthop-

tera, Coleoptera and Hemiptera (Table 5 ) . Spiders and

crabs were the main food items other than the insects.

The detailed gut content analysis showed that

R. hexadactyla feeds on annelids, arthropods, molluscs,

pisces, amphibians and reptiles. Among the annelids,

earthworm belonging to Megascolex genus formed food of

this frog. Species wise identification was not possible

due to the digested condition of earthworms. Among the

arthropods, insects formed the major food item of this

frog. Dragon fly and its nymphs were present in con-

siderable numbers. Pests 1 ike Labidura riparia,

Stomach contents of R. hexadactyla expressed as percentage of total body weiqht with respect to

sex and month

Month

January

February

March

April

May .- June .

- --1--G=.?-

Sex

Male ( % )

2.03

0.50

0.94

3.46 -

- - 1.07

0.45 ..

July - 2.11 1.49

---....... -.

Female ( % )

1.76 -.

0.44

0.15

1.29

1.11 -_ .----

0.74

August

September - .

November - -- 0.90

December 1.49 -.-.- - -

0.71 ..

0.30

0.48 -.- 2.61

2 3

Anisolabis sp. and Forficula sp. were also found in the

food. Among the orthopteran insects, Gryllotalpa fosser,

Gyllopsis sp . , Gymnogryllus sp . , Gry1.lus sp . , Oxya hyla

hyla, Spa thosternum calignosum , Hie.roglyphus banian,

Tryxalis sp. and Seclimena sp. were present. Most of them

are considered as serious agricultural pests. Carnivorous

water bugs like Spherodema annulattirm and S. rusticum

belonging to the order Hemiptera formed one of the most

favoured food items of this frog. Diplonychus sp.,

Nephotettix sp., Gerris sp. and tlhe members of the

hydrometidae family from the same order were also present

in the food item.

Among the Lepidopterans, caterpillars (unide-

ntified), Nectuid and Hesperid larvae formed the food of

this frog. Periplaneta americana was: the only member

representing the Blatteria order obtained from the

present study. Anopheles sp. of the Dipteran order was

another important food item of this frog. Other members

of the same order like Ochthera sp., Chironomous larvae,

Musca sp. and Parasarcophaga sp. were also present in a

low percentage. Camponautus compresses and Megachilla sp.

belonging to the order Hymenoptera. were found in con-

siderable numbers.

Members of the Coleopteran order were widely

distributed in the food content of this frog. Among them,

2 4

Anoplogeni us sp . , Bembidion soborium , Systellocrani us

sp . , Scari tes sp . , Cybister larva, Anomaila cholorocarpa ,

A. dussumieri, Onthophagus sp. , Hetronycehus sp. , Popilla

sp. , Sternolophus brachyacanthus, Gonocephalum sp . and

Coelophora sp. contributed the major portion.

Among the crustaceans, Palaemon sp., Paratel-

phusa bouvieri and P. hydrodromous were represented in

considerable numbers.

Order Arnaida formed one of the major

contributors to the food spectrum of this frog. Among

them, Paradosa songosa, P. bursantiensis, Paradosa sp. ,

Hippassa sp . , Lycosa iranii , L. suma trani;! , L. bistria ta ,

I'etrogna tha andamanensis, T. mandibula ta , Neoscona

legubris and Heteropoda sp. were present in good number.

Centipedes and millipedes from the class myriapoda were

also obtained from the gut contents.

Indoplanorbis exustus was the dominant mollusc

present in the gut content of this frog. Among the pis-

ces, Haplochilus punchax was obtained throughout the

study period in a lower percentage. Amphibians and rep-

tiles were occasionally present in the food spectrum of

this frog.

The order Opisthopora (earthworm) was found

high in the month of October. Anisoptera (dragon f l y ) wan

recorded in highest percentage in the month of June. They

2 5

were found to be totally absent in February. Dermaptera

(earwigs) was found high in January and Orthoptera

recorded highest percentage throughout the year. Hemip-

tera was found high in July and Lepidoptera found high in

the month of March. Members of the Blatteria order was

not a common food of this frog as evidenced from their

disrupted occurrence during the study period. They

recorded the highest percentage in the month of February

and December. Diptera was found to be totally absent in

the month of April and June. Members of the Hymenoptera

and Coleoptera were found throughout the year.

Decapoda and Aranida werte the two important

orders other than insects forming the food of this frog.

They were present throughout the year. Decapoda recorded

its highest percentage in March and Aranida dominated in

the month of June. Basommatophora and Systellommatophora

were also present in the food contents of this frog.

Among the vertebrates, fishes belonging to the

order Cyprinidontiformes were present throughout the year

in a low percentage. Cypriniformes and Perciformes were

asflumed to be incidental inclusions. Frogs and reptiles

were also found in the present study. Their occasional

occurrence suggested an accidental inclusion as a food

item.

Table - 6. Economically important organisms recovered

from the gut of R. hexadactyla

T o f the-r7Zpp- 1 konomic ----- -&awe 1 Dragon fly (adult & nyrrph) Carnivorous, Predator

~ a b i d u r i a ri ar ia Carnivorous, eats m l l insects

R-st

Pest on paddy

CXnnivorous

do.

ry harmful - to Paddy do.

'arnivorous water bug

do.

Harmful to crups

Water skater

Crop pest -

do.

Household pest

Vector

Fish food

Household pest

Nuisance to trees -- do. -- do.

do.

Paddy ~ s t

CrOF P S ~ ~

do. ..

do.

ster Larva Predacious

Table - 6 contd....

-

.

-

-.

Anomaila dussumieri

- -- A. chlorocarpa -. Autocerica insanabilis

Larval £ o m darnage roots of paddy and cereals -.

Pest of cashew ........ .- ....... ..........

do.

On t hopha gous

Holotrichia sp.

Hydrophilid sp.

Heteronychus sp.

Stgernolophus brachyacan thus

Melanot us h r i t icornis

Sipalus sp.

Gonocephal um sp.

Crop pest

do.

Larva predacious

Paddy pest

Pest of stored foodgrains .................

do.

- Crop ps t .

Paddy pst

Palaemon sp. .- - Para telphesa bo u vieri

P. hydrodromus

Paradosa songosa

P. bursantiensis

Lycosa i r an i i .-

L. sumatrana

L. b i s t r i a ta

Tetrognatha andamanensis

T. mandibulata - Nmscona legubris

Pila sp.

Haplochil u s panchax

Rasbora daniconius

Etroplus sp.

Rana cyanophlyctis

Useful

Serious paddy pest

do.

Biological control agent

do. .

do.

do. -.

do.

do. .- .

.ye--- do.

do.

Useful organism

Larvivorous biological control agent -

Edible f ish - do.

Useful ............

R. hexadactyla -

Typhlopus

Calotes sp.

Edible froy

Prerlator

Predator ............... .- ....... ........................ .................................................................. ............................................................................................

26

Vegetable matter, stones aind other debris were

also found in most of the stomach examined for the

present study. This is only an accidental inclusion.

The economic importance of some of the food

items is represented in Table 6. It was evident that R.

hexadactyla is a natural enemy of most of the agricul-

tural pests found in its habitat. This frog fed mainly on

paddy and other crop pests. Many of the serious paddy

pests like Gryllotalpa fosser, Oxya hyla hyla,

Hieroglyphus banian, Anoplogenius sp . , AnomaiJa dus-

sumieri, Heteronychus sp . , Gonocepha.lum sp . , Para tel-

phusa bouvieri and P. hydrodromous and other crop pests

like Nephotettix sp., Eborellia sp. , Nectuid larva,

Hesperid 1 arva , Bombidion soboriur;~, Scari tus sp . , Gnathophorous sp. , Onthophagous sp. , Holotrichia sp. and

Sipalus sp. were present in the food items. Likewise

Anopheles sp. was an important food item of this frog.

Pests of stored food grains like Sternolophus brachyacan-

thus and Melanotus hirticornis also formed the food of

this frog. Anomaila chlorocarpa, an important pest of

cashew, was also found in the food contents.

Some of the useful organisms were found in the

food spectrum of R. hexadactyla. They included fish food

organisms, prawns. fishes and some frogs. Some of the

biological control agents (Table 4 ) also formed the food

27

of this frog. But their proportion was very low when

compared to other harmful organisms consumed by this

frog.

R. hekdac ty la is found very often in water and

its more aquatic habit shows that a greater number of

aquatic insects are being eaten by it. Movement of the

prey attracts attention of this frog and the first reac-

tion is to jump upon and swallow its prey, all in a

single movement. The frog may detect: the prey from some

distance and then approach it in a series of bounds, the

last leap being made onto its prey. The forelegs are used

to push into the mouth any item which it may not be able

to swallow completely. The occurrence of paper, bits of

grass, leaves and stones in their stomach is no doubt due

to their being taken in accidentally and they remain

undigested.

The present study reveals that R. hexadactyla

feeds on insects, crabs and spiders along with some

vertebrates. The frog's capture of these organisms is a

chance factor. The representation of these organisms

mainly from aquatic habitat showed the affinity of this

frog to such environments. Further, cannibalism noted in

the present study agrees with the observations of

Boulenger (1897) and Noble (1918) that frogs and toads

are carnivorous and cannibalistic. The seasonal dietary

requirements of the frog varied (Table 2 ) . The high food

consumption per frog in May - August is because of the

high reproductive activity of the frog during the season

(see Chapters 4 and 5 ) .

The food spectrum obtained in the present study

indicates that insects formed the main diet. From the

observations recorded in the present study, it can be

noticed that insects, spiders, crabs are the major food

items. Arthropods form the bulk of the diet of R.

hexadactyla. Amongst the arthropods, insects appear to be

the most favoured food of this frog. Some of these in-

sects are of great economic importance. Issac and Rege

(1975) and Abdullali (1985) have reported that R.

t igerina plays a significant role in controlling agricul-

tural and other pests in the field. Crabs are found in

large numbers in the diet of this frog. They are often

seen in the paddy fields and cause damage to the bunds in

the fields by boring holes in them. Crabs are found as

one of the major pests of paddy (Kadam et al., 1960) and

are known at some stages of their life to feed on rice

seedlings both before and after transplanting. The frog

is thus very helpful in keeping the population of crabs

2 9

harmful to agriculture in check. S'ome gastropods were

recorded from the stomachs of a few specimens. The ver-

tebrate groups such as pisces, amphibia and reptilia are

also represented in the food of this frog, but there is

no reason to believe that they form regular items of the

diet (Andrews, 1979).

The presence of stones, leaves and debris among

the gut contents of R. hexadactyla sh~ows that the above

materials might have been engulfed accidentally along

with the prey. Vegetable matter occurred in many guts,

but the amount was quite small and may thus be well

explained as inadvertently ingested with the food. The

intake of pebbles and plant matter may be important in

providing roughage as well as increased grinding capacity

for the total mass envelope. The presence of stones and

vegetable matter in the guts of anlurans has also been

reported by earlier workers (Taylor, 1958; Berry and

Bullock, 1962; Berry, 1965; Joshee, 1968; Krameck, 1972;

Andrews, 1979; Battish et al., 1989; Sreelatha et al.,

1990).

Mondal (1970) observed that. the "northern race"

of R. hexadactyla is a herbivore while the "southern

race" prefers animal food and preponderates over

vegetable matter. The present st.udy indicates that

3 0

R. hexadactyla i.n this part of Kerala is carnivorous and

it agrees with the observation of Andrews (1979).

According to Jensen and Klimstra (1966). Hedeem

(1970) and Nigam (1979), anurans are opportunistic

feeders and consume the most readily available food. The

more frequent occurrence of this frog in the aquatic

medium may be attributed to the easy availability of

prey. Also there seems to be a correlation between the

abundance of frogs and the paddy field fauna. However,

Sweetman (1944) and Brower and Brower (1962) found that

anurans were capable of developing food preferences.

Individuals of a particular species may exhibit sig-

nificant differences in the kinds and amounts of prey

eaten in different habitats; this mainly reflects dif-

ferences in prey availability among habitats. Inger and

Marx (1961) found noticeable di:Eferences in stomach

contents of frogs in the Upemba National Park in Zaire,

and Barbault (1974) noted differences in diets of anurans

in savanna and forest habitats in the Ivory coast. Dif-

ferences on a more local scale also are evident. For

example, in freshwater habitats, the diet of Rana

cancrivora consists mainly of insects, but in nearby

brackish water the frogs eat mostly crustaceans (Elliot

and Karunakaran, 1974). Seasonal differences in diets

have been reported for various species of amphibians such

3 1

as Rana pretiosa (Turner, 1959 ) ; Not:ophthalmus virides-

cens (Burton, 1977) and Plethodon ylutinosus and P.

jordani (Powders and Tietjen, 1974). Surveys of diets of

many anurans in a tropical seasonal environment in west

Africa revealed noticeable differences throughout the

year (Inger and Marx, 1961). The seasonal activity of

certain species is determined, in part, by the activity

of the prey. This is especially evident among prey

specialists. The activity of the termite eating anuran,

Breviceps verrucosus in south Africa is timed to the

swarming of termites (Poynton and Pritchard, 1976).

In the present study, a seasonal variation in

the food organisms was reported. This can be correlated

with the prey availability in the area where the frog

lives. This seasonal variation is precise because the

climatological conditions prevailed in this region are

favourable for the multiplication of insects and other

organisms throughout the year which is reflected in the

diet of this frog. The present study reaffirms that frogs

are useful as control agents for various insect pests

especially those which are considered as serious crop

pests. Though frogs are opportunistic feeders, their

Eeeding on many phytophagous insect pests does support

their usefulness ae biocontrol agents. A number of ear-

lier workers like Gadow (1901). Pack (1922). Kadam and

32

Patel (19601, Stiles et al. (1969), Fellow (1969),

Andrews (1979). Abdullali (1985), Battish et al. (1989)

and Sreelatha et al. (1990) also stressed this fact.

The present study on the food of Indian green

frog, R. hexadactyla reveals that the frog feeds mostly

on insects, ants and spiders, most of which do not belong

to the beneficial group. Thus, this species may be con-

sidered as a useful amphibian for the control of pests

and other insects, and thus plays a very important rolc

in the economy of nature. So, the removal of large num-

bers of frogs from their environment will upset the

existing balance of nature and in cultivated areas the

process is highly detrimental to crops. It is now

generally accepted that biological control is the safest

and only method which does not produce any harmful reac-

tions, and the removal of large number of frogs disturb

this natural process.

--o--