Herpetology: Chapter 8

What is home range?

area where individual can move about without defending from conspecifics. In herps this is usually associated with resources and can vary through time and space

Home range can change over time and space and is related to microhabitat

Discuss this image

the circles represent populations of turtles and the open ones are 1-2 months after. This shows how some herbs, like the soft-shell turtle can change location of home range without any change in habitat

• river shift is typically linear because it is confined by geography (terrestrial does not have this confinement)

Discuss this figure

overall idea: Home range size can vary among sexes and with reproductive state.

In Sceloporus jarrovi (as seen in the figure), females home range stays the same across time. Females have a consistent home range size while males have an increase in home range during the fall. This is because of breeding season, males will increase home range to increase chances of mating

Describe this graph

Overall: in most species, home range size generally decreases as food availability or density increases.

As females increase in density, home range size decreases. This happens because the amount of area available is fixed, cannot change the amount of terrestrial area.

Describe this figure

In Sceloporus merriami home range of males is larger than those of females, but geographically close populations vary greatly in home range size.

This figure shows home range sizes across the years. Noticed that males have a larger home range regardless of site and there is lots of variation across the years

Describe the environmental constraints of the Boquillas

There is limited variation due to a very hot and dry climate. The environment thermally constrains the animals living in it. Temperature affects home range and can put constraints on metabolism, hydration, and food availability.

Describe this image

Freshwater environments offer special challenges in terms of space use, it is both 3D and fluctuates based on rainfall or drought.

Flooding changes home range, there is an expansion when water recedes.

Animals might estivate during drought periods

When an animal is aquatic / semiaquatic rain can be great, but drought can have a serious impact.

Migration of water pythons

Water pythons migrate seasonally to follow their prey, shifting home range. This migration is driven by rain which influences the avaliability of food sources which come from the water.

Describe the connection between evolutionary history and behavior of moving and defending home range.

Behavior of moving/defending home range is evolutionary inertia. We see some, but limited changes to it.

Evolutionary history determines a large part of behavioral patterns in territoriality. Shifts are seen in phylogeny.

Describe this figure

ancestors of these lizards defended entire home range then a split occurs where skinks (in red) defend specific sites in home range and where another group (the blue) where there is no defense at all. Then a split to Iguanids displays defense to entirety of home range again.

Overall this figure displays a shift from defending entire home range to decreased defense to a return of this trait.

How do substrate characteristics influence animals?

They can constrain the way that animals use particular habitats. This determines community structure and predator-prey dynamics

There is a pattern of evolutionary drive for ____.

patterns of defense

Aggregation

Animals working together in their home range.

• Tadpoles form dense pools and schools that increase chances of survival

• Salamanders aggregate in damp areas when ground becomes too dry

• Many herbs brood or guard nests and remain near until the eggs hatch (paternal effect)

What general kinds of factors influence movement of herps? What is the most apparent dichotomy?

Both intrinsic and extrinsic factors.

Most apparent dichotomy (division) in movement is between diurnal vs. nocturnal. (turtles can be both)

Daylight and temperature

Impacts how animals move in home range.
Ectotherms are especially picky about extent of heat experience. Lizards in Florida prefer morning and evening.

What does long range movement look like in herps?

Can differ

many animals will return to their home ponds, indicating that some movements are not immigration.

Amount of movement seen in turtles

Turtles’ amount of movement was measured from ponds to sites in area to notice how far would they be willing to travel. Males would travel further than females. Further the distance, the less / decrease in amount of females to males.

Mass migration of sea turtles

An exception to the ability for amount of movement differing.

Mass migration is an exception.

Sea turtles love to migrate, they will go to the beach to lay eggs. Sea turtle mass movement is directional; in one direction, it is intentional and not random. There are well-defined beginnings and ends. These animals store energy for this movement to make the journey (also seen in birds), aloted energy.

Migration in amphibians

Amphibians will move out of pond and return to the same pond to lay eggs. There is a high level of mortality in amphibians compared to turtles because of human involvement. Dispersal occurs post-metamorphosis because there is a physiological constraint that needs to be overcome with development of legs. Migration distances varies over years, there is no specific pattern.

What is migration vs. dispersal?

Migration: A → B, with return

Dispersal: A - → anywhere without return, it is undirected to unknown locations

What is an example of dispersal?

In amphibians, juveniles leave to find own home (amphibian metamorphs)

Hatching sea turtles

How does dispersal relate to home range?

Drives home range/ population expansion for species.

Rainfall can create opportunity for mass dispersal in amphibians

What are evolutionary driving forces that result in dispersal?

• Habitat instability- if habitat experiences change, may create reason to leave

• Intraspecific competition

• Inbreeding depression- Dispersal becomes beneficial if there is an issue of inbreeding because genetic variability is needed

Describe the cost-benefit system of dispersal

Three major components: inbreeding, habitat, and intraspecific competiton

-: cost

+:benefit

Philopatry favoring

desire to stay where a population is currently at

Special dispersal in frogs

several species of frogs in unrelated clades transport eggs or juveniles on backs and most will drop the eggs off in one place

Can look for environments to protect against predation

What are the major orientation devices? What tools do they directly or indirectly provide for an animal?

Olfactory system: use of odors (such as pond odors or local odor patterns)

• indirectly create a map and pilot

Eyes and pineal complex: use of sun, moon, stars, skylight polarization

• directly create clock and compass and pilot

• indirectly create map

Magneto-reception: use of earth’s magnetic field

• directly create compass

• indirectly create map

Auditory system: chorus of conspecifics

• directly pilot

Describe this figure

Overall concept: many herps return to specific shelters following both short and long distance movements

Coluber viridiflavus has single day loops, several day loops and large loops lasting up to a month

Describe this image

Interface between aquatic and terrestrial environments provides a landmark for orientation by animals that use the interface.

This shows an example of Y-axis orientation in frogs. Jumping into water at 90 degrees to shoreline, frogs use the sky to orient themselves with respect to the environment

Frog almost always oriented 90 degrees from water to protect from predation, tadpoles can orient 90 degrees toward shore to do the same.

Describe Newt orientation

Newts orient to shore primarily through visual cues. They use the sky, but also depend on the specific type of light available

• full-spectrum of visible light they can correctly orient

• short wavelength only they can correctly orient

• long wavelength only they are unable to orient

Orientation of alligators and sea turtles

Alligators and sea turtles can orient based on magnetic cues.

Direction of waves as it hits the beach at an angle can be useful for turtles to orient themselves. They can detect changes in motion of the waves and can feel acceleratory effects of waves on their bodies.