PHOTOS OF FROGS

FROG POPULATION IS DECLINING

INFORMATION ON FROGS
Frogs are amphibians in the order Anura (meaning “tail-less”, from Greek an -,
without +oura, tail). Most frogs are characterized by a short body, webbed digits
(fingers or toes), protruding eyes and the absence of a tail. Frogs are widely
known as exceptional jumpers, and many of the anatomical characteristics of
frogs, particularly their long, powerful legs, are adaptations to improve jumping
performance. Due to their permeable skin, frogs are often semi-aquatic or inhabit
humid areas, but move easily on land. They typically lay their eggs in puddles,
ponds or lakes, and their larvae, called tadpoles, have gills and develop in water.
Adult frogs, follow a carnivorous diet, mostly of insects like grasshoppers, beetles,
bugs, water insects, earthworms and snails. Frogs are most noticeable by their
call, which call, which can be widely heard during the night or day, mainly in their
mating season which often falls during the rainy season.
Agricultural landscapes, although often highly altered in nature, provide habitat
for many species of amphibian. However, the persistence and health of
amphibian populations are likely to be compromised by the escalating use of
pesticides and other agricultural chemicals. Preliminary evidence suggests that
chemical-use many affect frog populations within irrigation areas.
Frogs play a pivotal role in ecosystem as secondary consumers in many food
chains. Tadpoles have significant impact in nutritional cycling. They are
herbivorous to omnivorous and are the prey items for both invertebrates and
vertebrates. Adult frogs are the best biological pest controllers. Because of their
importance in agricultural ecosystem, decline or extinction of their population has
significant impact on other organisms along with them. The insect pest outbreak
often occurs due to decline in frog populations of agricultural fields.
From the ecological perspective, amphibians are regarded as good ecological
indicators. Due to high degree of sensitivity, either during tadpole stage or as
adults, they respond to very slight change in the environment. Such responses
have been used to indicate habitat fragmentation, ecosystem stress, impact of
pesticides, and various anthropogenic activities.
Frogs have been a good food source and few years ago India dominated the
frogleg exports (it is completely banned now) along with Southeast Asian
countries. They are exploited as model organism in ecological, embryological,
physiological and genetic research. Poison dart frogs of Dendrobatidae family
have highly toxic skin compounds that area smeared to arrowheads to kill larger
animals.
From the past two decades, amphibians have gained much importance for the
declines in their populations worldwide. There are clear evidence for such
declines from North, central and South America, Europe, Africa and Australia.
Global amphibian decline can be attributed to those with obvious causes like
habitat destructions, alteration, fragmentation, climate change, radiation,
chemical contamination, pollution and diseases of viral, fungal, bacterial infections
as evident from various parts of the world and those mysterious declines with no
obvious cause. Looking from another perspective, the threat to the amphibians
can be attributed the changes in physical environment and biotic environment.
Changes in the physical environment include Ultra-Violet (UV) radiation, climate
change, acid rain, pesticides, herbicides and fertilizers, where as the biotic
environment includes, fragmentation, demographic effects (barriers for the
movements of one population to other), genetic effects (fragmentation enhances
isolation, isolation emphasizes inbreeding, inbreeding results in stress, stress
reduces viable population), diseases and synergistic interactions.
Different types of frogs are susceptible to different diseases. Chytridiomycosis is
an infectious disease of amphibians, caused by the chytrid Batrachochytrium
dendrobatidis, a non-hyphal zoosporic fungus. Chytridiomycosis has been linked to
dramatic population declines or even extinctions of amphibian species in Western
North America, Central America, South America, Eastern Australia and Dominica
and Montserrat in the Caribbean. The fungus is capable of causing sporadic
deaths in some amphibian populations and 100% mortality in others. There is no
effective measure for control of the disease in wild populations. The disease is
contributing to a global decline in amphibian populations that apparently has
affected 30% of the amphibian species.
Due to the process of global warming (rise in earth’s mean temperature), drastic
changes in the climate occur. This leads to the decreased depth of pond water,
increased intensity of UV-B radiation. Which ultimately reduce the immune
system of the amphibians. Due to this amphibians are more prone to diseases
and death.

Possible factors influencing population Decline of Frogs:

changes in Physical Environment:

Factors

UV-B radiation

Climate change

Acid

precipitation

and soil

Pesticide (eg;

malathion,

atrazine etc.),

Fertilizer and

Chemical

contamination

Effect

UV-B damages DNA and/ or kills cells, causing egg mortality,

lesions, and increased susceptibility to disease and low pH.

The changes in the climate (due to global warming) can lead to

decreased depth of pond water and increased intensity of UV-B

radiation. This ultimately reduces the immune system of

amphibians. Hence they will be more prone to diseases.

Toxins create barriers to dispersal and cause high egg and larval

mortality.

Toxins cause direct mortality of eggs and adults, mimic

endocrine hormones, reduce the prey

Changes in Biological Environment:

Factors

Habitat

modification,

fragmentation

Introduced

species

Disease

Biological

Interaction

Effect

Deforestation and agriculture; wetlands are drained and filled.

Roads, introduced species, and low pH dissect habitats, creating

barriers to dispersal.

Introduced predators, prey on/or compete with native

amphibians.

Disease often causes death in amphibians; what made

amphibians susceptible to disease is often unknown.

Uphill migration of birds and lizards with rise in cloud cover

elevation