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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--