Transcript No Slide Title

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