1. Amphibian Life History

2. Amphibian Life History
What is an amphibian?
Amphibian evolution
Ecological importance
Feeding behavior
Vocalizations

3. What is an Amphibian? From the Greek - Amphibios - leads two lives
Ectothermic vertebrates with aquatic, gilled larval stage and terrestrial adult stage. All possess glandular skin and lack nails or claws.
Kingdom - Animalia
Phylum - Chordata Subphylum - Vertebrata
Class - Amphibia
Order Caudata – Salamanders 390 spp
Order Anura – Frogs and Toads 4000 spp
Order Apoda – Caecilians 163 spp

7. Evolution
Evolved from Lobe-finned fishes common in Devonian Period mya
During Devonian, sea levels rise and fall repeatedly; coastal area swamps flood and dry many times.
Characteristics
Lungs
Some possessed true internal nares
Fins supported by bony elements

8. Geological Time Era Period Epoch MYA Major Events Cenozoic Quaternary
Recent
0.01
Repeated glaciations, us!
Pleistocene 2
Large mammal extinctions
Tertiary
Pliocene 12
Radiation of birds,
Miocene 25
mammals, angiosperms,
Oligocene 36
continents assume current
Eocene 58
positions.
Paleocene 63
Mesozoic
Cretaceous
135
Mass extinctions at end
Jurassic
181
Dinosaurs abundant, birds
mammals, angios appear
Triassic
230
First dinosaurs, continents
begin to drift apart
Paleozoic
Permian
280
Pangea; amphibs decline
Carboniferous
345
Amphibs, insects diverse
Devonian
405
1st amphibians, insects

10. Evolution Amphibians diverse by close of Devonian – 345 mya
Key evolutionary traits/adaptations
Most return to water to breed – aquatic larvae have gills
Moist skin aids in respiration
Improved circulatory system
Toxic skin glands offer protection
Sensory regions of brain processing vision,hearing,balance expanded compared to fishes
Locomotion - salamanders less efficient; anurans capable of hopping, jumping, become most successful group

11. Ecological Importance
In many moist, terrestrial habitats, amphibians may be the most important links in the food chain
Amphibians may exceed in numbers and biomass each of other vertebrates
Annual production of new tissue exceeds birds, mammals
Salamanders in NE had densities of 7-10/sq m; 2X biomass of breeding birds, same as small mammals
In Michigan marsh, amphibians most important 2nd and 3rd level consumers in food chain
In Texas, standing crop of Lesser Siren greater than that of total of 7 species of fish in same habitat

12. Ecological Importance
Amphibians are the primary vertebrate predators on small invertebrates in many freshwater and moist terrestrial environments
A small pond population of cricket frogs (Acris crepitans) estimated to consume ~ 4.8 million arthropods/yr
Amphibians are major conveyor belt of energy transfer from arthropods to other vertebrates
Amphibians have low metabolic rates, slow maturation and are relatively long-lived, thus serving as energy reservoir for ecosystems

13. Food Habits
Most adults are carnivorous, feeding on a variety of live animals – anything they can swallow!
Larvae mostly herbivorous – algae, plant material, debris
Tongues of many species can be extended well beyond opening of mouth
Sticky pad impacts on, adheres to and pulls in prey
Action is so fast—10 msec—as to be nearly undetectable by human eye

14. Vocalizations Male anurans use ADVERTISEMENT CALLS to attract females
Vocal sac(s) modify, amplify sound as air forced from lungs over larynx
Call intensity varies with species – audible from several yards to over a mile. SPL: dB
Energetically expensive - O2 consumption up 4-7X
Intensity may be related to spacing of local males

15. Anuran Distended Vocal Sacs
Pseudacris
Bufo
Rana

16. Vocalizations Chorus Formation
Advertisement calls first attract other males, then females
Calls often alternated when males close to each other
Tendency to call in groups of 2-4 with “choir master” always initiating, each with noticeably different quality
Dominant males call louder, longer, lower pitched - may reflect age, size, vigor - all factors in female selection

17. Vocalizations Warning Calls/Release Calls
Vocalizations cease or are modified under threat of predation
Fright calls often given before jumping into water
Release, distress calls given if anuran grabbed by wrong sex or if captured by predator

18. Amplexus - the mating position of frogs and toads, in which the male clasps the female about the back
Amplexus