AMPHIBIAN LIFE HISTORIES

I. AMPHIBIAN LIFE HISTORIES I.WHAT IS AN AMPHIBIAN? II. AMPHIBIAN EVOLUTION III. ECOLOGICAL IMPORTANCE IV. FEEDING BEHAVIOR V. VOCALIZATIONS

I. WHAT AN AMPHIBIAN IS 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

II. EVOLUTION Evolved from Lobe-finned fishes common in Devonian Period - 400 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

II. 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

III. 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

III. 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

IV. 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 - 10msec - as to be nearly undetectable by human eye

V. 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: 90-120 dB Energetically expensive - O2 consumption up 4-7X Intensity may be related to spacing of local males

Anuran Distended Vocal Sacs Pseudacris Bufo Rana Anuran Distended Vocal Sacs

V. 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

V. 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

Amplexus