Why is a song written by many frogs better than a song written by only one frog

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• Why is a song written by many frogs better than a
  song written by only one frog?

Ans Because many frogs make a Chorus!
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The Grim Reality

• WIDE SPREAD OF AMPHIBIAN DECLINE WORLDWIDE
• History
• 1989 First World Congress of Herpetology
• 2004 World Conservation Union Global Amphibian
  Assessment (GAA)
• 1896 (32) species threatened
• 2468 (gt 43) species declining

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(www.globalamphibians.org)
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Causes for Amphibian Decline

• Kira Jang
• BIOL 402
• November 14, 2006

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Outline

• Amphibians what are they?
• Why we care
• Causes of Amphibian decline
• Human Impact
• i. Direct
• ii. Indirect
• UV b
• Diseases
• Invasive Species
• Climate Change
• Complex Causes Integration Theory
• Prevention of Amphibian Decline
• General Problems with present research

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Amphibians 101

• Phylum Chordata
• Class Amphibia
• Order Anura (Frogs Toads)
• Order Caudata (Salamanders Newts)
• Order Gymnophiona (Caecilians)

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• General Characteristics
• Cold-blooded
• Oviparous
• Undergo metamorphosis

Adult
Larval Stage

• Terrestrial
• Lungs develop

- Usually aquatic
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• General Habitat
• Moist
• Freshwater environment to breed court
• Highest diversity Tropical Rainforest

(www.globalamphibians.org)
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Why we care

• Indicators of environmental health/stress
• Land and Aquatic
• Moist, permeable sensitive skin
• Unshelled eggs
• Predator/ Prey interactions (adults), herbivores
  (larva)
• Food
• Education

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Causes for Decline

• a) Human Impact
• i. Direct
• - Food
• - Education
• ii. Indirect
• - Habitat destruction (farming, road
  
• contruction, herbicides/pesticides,
  
• pollutionacid rain)
• significant impact on decline?

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Causes for decline a) Human Impact

• CASE STUDY 1 Roads (Hels Buchwald, 2001)
• Roads- direct effect (road kill)
• - indirect effect (habitat
  fragmentation)
• Purpose Probability of getting killed depending
  on
• a) velocity of animal
• b) diurnal pattern
• c) traffic intensity
• What proportion does this represent?

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Causes for decline a) Human Impact

• CASE STUDY 1 Roads (Hels Buchwald, 2001)
• RESULTS
• 34-61 chance of death
• (Traffic load 3207/d)
• 10 of population
• cross road

600m
8m
6 species tracked 2 newts, 2 frogs, 2 toads
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Causes for decline

• b) UV b radiation (290-320nm)
• - biomolecules absorb UVb more efficiently than
  white light
• CAUSED BY Stratospheric ozone depletion
  (anthropogenic, CFCs etc)
• EFFECTS
• 1. stress associated with damaged DNA
• 2. affect hatching success

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Causes for decline b) UV-B

• CASE STUDY 2 Repair Mechanism and Hatching
  Success (Blaustein et al., 1994)
• Purpose To measure the effect of UV-B on
  amphibian decline by (1) measuring level of
  photolysate and
• (2) hatching success.
• Photolysate photoreactivating enzyme that
  repairs UV-damaged DNA
• Study Organisms 1. Pacific Treefrog (Hyla
  regilla)
• 2. Western Toad (Bufo Boreas)
• 3. Cascades Frog (Rana cascadae)

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Causes for decline b) UV-B

• RESULTS
• Photolysate levels
• Hatching Success
• CONCLUSION Decline due to UV-b is related to
  amphibians ability to recover from exposure

significance
Hyla. Rana. Bufo.
(Blaustein et al., 1994)
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Causes for decline

• c) Diseases (viruses, worms, fungi)

PATHOGEN
EFFECT
Egg mortality Synergistic effects with UV-B
(Kiesecker Blaustein, 1995)
Saprolegniaceous Fungi
Infamous in adult amphibiansimpair cutaneous
resp. osmoregulation Weaken immune
(Berger et al., 1998)
Batrachochytrium dendrobactisdis (Chytrid Fungus)
Ribeiroia ondatraeis (Trematode Worm)
Leg deformaties
(Johnson et al., 1999)
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Causes for decline c) Diseases

• CASE STUDY 3 Trematode worms causing Leg
  deformaties (Johnson et al., 1999)
• Purpose
• Measure survivorship of Pacific
• treefrog tadpoles exposed to
• Trematode worms

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Causes for decline c) Diseases

• RESULTS
• Increased density of trematode decreases
  survivorship and increases abnormalities
• Dissection of abnormal limbs found trematode

_____ SURVIVORSHIP FREQUENCY -------- ABNORMALITY
FREQUENCY
(Johnson et al., 1999)
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Causes for decline

• d) Invasive species
• CAUSED BY usually fish or other amphibians
• EFFECTS
• 1. Direct interspecific interaction
• (predation or competition)
• 2. Indirect hybridization or carrier of
• pathogens

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Causes for decline d) Invasive spp.

• EXPERIMENT
• 2 adjacent fishless undisturbed lakes
• 1 stocked with trout in deep water
• Larvae of Mountain yellow-legged frog (Rana
  muscosa) occupy deep water bodies
• RESULTS
• Increased trout decreased frogs

(Knapp Matthews, 2000)
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Causes for decline

• e) Climate Change
• CAUSED BY ex. Increase Global mean Temperature
  (0.6ºC)
• EFFECTS
• (1) Change in breeding phenology
• (2) Reach limits of temp. or moisture

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Causes for decline

• f) Complex Causes
• Ex. 1 Precipitation Shallow Pools
• UV-B exposure and Fungi
• (Kiesecker et al., 2001)
• Ex. 2 Pesticides, agricultural runoff
• Trematode deformaties
• (Pakhala et al., 2003)
• - Moving towards Multifactorial Approaches for
  amphibian decline

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Prevention of Amphibian Decline

• Must first understand cause
• BUT amphibians in captivity for care
• Is this enough?

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General Problems and Future Directions in Research

• Skeptical of importance of amphibians
• Stricter standards for experiments (some not long
  enough, or not generalizable)
• Apply theoretical approach in small popns
• Prove by reintroduction of amphibians in declined
  areas after relieving cause
• Experiments modelling to find cause
• High mortality doesnt necessarily decline
• Relief of density-dependent pressures
• So, far may experiments of correlation only

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References

• www.globalamphibians.org
• Will be uploaded later, sorry

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• Any Questions?

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Declining?

• Populations or within populations
• In general world population
• Declining - data

(Houlahan et al., 2000)