BIOL 3300 Vertebrate Zoology:
Ectotherms - Herpetology
http://www.amphibian.com.au/
Why do herpetofauna move?
Benefits
Costs
Why do herpetofauna move?
Intrinsic factors
Extrinsic factors
Generalizations:
• Males move more than females
• Larger bodied animals move more than small animals
• Density of resources inversely correlated with home
range size
• Foraging styles impact movements
How can movements be determined?
• Need to be able to recognize
individual animals
• Need to be able to relocate
animals over time
How can movements be determined?
• Scale clipping
• Thermal/Freeze branding
How can movements be determined?
• Visible Implant Elastomer (VIE)
How can movements be determined?
• Visible Implant Alphanumeric tag (VIA)
How can movements be determined?
• Toe clipping
How can movements be determined?
• Passive Integrated
Transponder (PIT) Tags
How can movements be determined?
• Radio tracking…
How can movements be determined?
How can movements be determined?
Visualizing rattlesnake movements
John Lee
North
2 km
Spotted Frog Movements in the
Bighorn Crags
David Pilliod
Fishless Lakes
0
.5
1
Kilometers
How can movements be determined?
• Harmonic radar…
How can movements be determined?
• Spool and thread
How can movements be determined?
• Fluorescent powder
Figure 8.12 The snake Enhydris plumbea in Malaysia (Borneo) moves very little. The method of collecting movement data influences the results and might lead to
misleading conclusions in species that move considerable distances. Adapted from Voris and Karns, 1996.
What types of movements are there?
• Foraging (direction? distance?)
• Dispersing (direction? distance?)
• Migrating (direction? distance?)
Dermochelys coriacea
• Local Movements/Homerange (direction? distance?)
Turtles (fresh water) 500 to >200,000 m2
Snakes (Colubridae) ~10 to >200,000 m2
Snakes (Viperidae) 800 to 60,000 m2
Lizards ~15 to 1,000 to 20,000 m2
Anurans 1 to ~2,000 m2
Urodelans 0.1 to ~90 m2
What accounts for the difference in
movements/home ranges?
• High fidelity to no fidelity
• Factors might include:
• Feeding niche
• Size
• Resources
• dispersion
• density
• renewal rate
Crotaphytus collaris
Aspidoscelis tigris
Figure 8.2 Seasonal variation in home range size for male and female Sceloporus jarrovi. Breeding occurs in fall, at which time male home ranges increase in size.
Adapted from Ruby, 1978.
Figure 8.3 As female density increases, home range size decreases for most amphibians and reptiles, as shown here for territorial and nonterritorial female lizards.
Adapted from Stamps, 1983.
Figure 8.4 Home range size in Sceloporus merriami varies between sexes, among years, and among three different sites in the Chisos Mountains of west Texas.
Boquillas, the site with the most extreme (hot and dry) environment, imposes thermal constraints on lizard activity, resulting in small home ranges.
Adapted from Ruby and Dunham, 1987.
What influences territoriality?
• Intermediate levels of patchiness, abundance and
high renewal rate.
• Home range defense is common only in sit-and-wait
insectivorous lizards.
Is the way to a lizard’s heart through his stomach?
Figure 8.7 Phylogeny for lizards showing the evolutionary distribution of home range defense. The ancestor of all lizards presumably defended the entire home range
with an overall reduction in area defended as lizards diversified, and this behavior is carried through in clades indicated by black. Site defense (clades in red) evolved in
the ancestor to Autarchoglossans. A lack of home range or site defense evolved independently twice, in the ancestor to the Lacertiformes and in the ancestor to
Anguimorpha. Taxonomy has been revised for consistency, but relationships to behavioral traits remain unchanged.
Adapted from Martins, 1994.
What about Migrations?
• Annual movements to and from areas some
distance away…
Examples/Reasons?
• Amphibian migrations
• Anurans < 1,500m
• Urodelans < 500m
• Often exhibit high
site fidelity!
Agalychnis spurrelli
What about Migrations?
• Terrestrial reptile migrations
• More rare… (example Galapagos Land Iguanas)
• Marine reptile (Sea Turtle) migrations
• Can be several thousand kilometers!
Eretmochelys imbricata
What about Migrations?
• Marine reptile (Sea Turtle) migrations
• Arribadas in Costa Rica
What about Migrations?
• Marine reptile (Sea Turtle) migrations
• Arribadas in Costa Rica
What about Migrations?
• Migrations to overwintering sites
• Anurans and fresh water turtles may move from
ponds to streams (Why?)
• Communal dens (hibernacula)
Figure 8.15 Model showing the relationships between costs and benefits of dispersal. The curved surface represents points where costs and benefits of dispersal are at
equilibrium. Dispersal behavior will be selected above the plane, whereas philopatry will be selected below the plane. The three-dimensional volume represents a
species in which some individuals (e.g., juveniles) disperse and others (e.g., adults) remain where they are. Adapted from Clobert et al., 1994.
Figure 8.16 Some amphibians carry their tadpoles or young around and aid in their dispersal. The Australian microhylid, Sphenophryne cornuta, drops off its young in
different places. Photograph by Stephen J. Richards.
What about Homing behaviors?
• Returning to home range when displaced…
• Urodelans (~50-60m up to 2Km)
• Anurans (~40-100m up to 100-1.6Km)
Taricha torosa
Bufo (Anaxyrus) terrestris
What about Homing behaviors?
• Returning to home range when displaced…
• Testudines (~300m up to 280Km)
• Crocodylia (3 to 30 Km)
Chelonia mydas
• Sauria (3 to 30 Km)
• Serpentes (3 to 30 Km)
Caiman crocodilus
What cues are used in Homing?
• Visual cues (visibile light, IR, UV, polarized, celestial)
• Chemosensory cues
• Y axis orientation (Magneto-taxis or photoperiod)
Figure 8.17 Relationships among cues, sensory systems, and the mechanistic basis of orientation and navigation for anurans. These relationships may be similar for
most amphibians and reptiles. For terrestrial species, odors might be associated with den sites or daily retreats. Adapted from Sinch, 1990.
What cues are used in Homing?
Figure 8.21 Different orientation cues believed to guide hatchling Loggerhead sea turtles from their nests on beaches in Florida to the open ocean. Lines indicate
direction of waves. Adapted from Lohmann et al., 1997, and Russel et al., 2005.
Figure 8.22 Life cycle of the green sea turtle showing the course of movements throughout life and possible cues used for orientation during each life history stage.
Adapted from Miller, 1996.