How is sexual activity triggered in Anolis?

• Sex hormones: testosterone in testes and estradiol in ovaries

• Testosterone injections induce courtship activity in castrated males with no prior courtship activity; estradiol injections induce sexual activity in females with ovaries removed

• Females exposed to springlike conditions began producing eggs; females in the field not exposed to springlike conditions did not.

• Females exposed to breeding males began producing eggs much earlier than did females that were alone, with other females, or with castrated males.

• Females exposed to breeding males whose dewlaps had been surgically removed were slow to produce eggs

• These are proximate causes for breeding for female anoles

  

• What about ultimate cause? — sexual selection

• Males show dewlaps more often in the presence of females — over evolutionary time, males that show dewlaps more often breed more

• There’s intersexual selection on dewlap and pushups, but there’s intrasexual selection on pushups too! Frequency of pushups increases around other males

3. Migration

• Proximate level: how do animals know where to go in moving from one seasonal “home” and another?

• Ultimate level: what are the fitness benefits of having more than one home range that could outweigh the costs of long-distance migrations?

• Motivations: moving with food sources, insects and small birds need to move to warmer places

Navigation - Proximate Cause of Migration

• Piloting — memorizing landmarks and locations of buildings

• Compass orientation — using the Earth’s magnetic field and location of the Sun, and where the tides are moving to orient themselves. Animals are much better at this than we are typically

• True navigation — really hard. Very few organisms use this. Going to an exact point

• Most animals use a mix of the first two

Why migrate? Ultimate cause

• Arctic terns feed on fish that are available in different parts of the world at different seasons. Thus, you could starve if you don’t migrate.

• Birds and fish breed in a different area than they carry out the rest of their lifecycle and thus need to migrate to that place. Could be advantageous to go somewhere with less predators and more food that the babies can eat.

4. Communication

• Communication — a signal is sent and received

• Honeybee communication — directional butt waggles

• Length of the waggle is proportional to how far away the food source is

• The direction of the waggle is what direction the food source is

• Direction is dictated by the position of the Sun — i.e the food source is at a 90 degree angle to the Sun