lab 9: predation

What is predation?

A "+/-" interaction where one organism (the predator) consumes another organism (the prey), benefiting the predator and harming the prey.

How do predators influence prey populations?

Predators regulate prey populations by influencing their size and growth rate.

How do prey influence predator populations?

Prey regulate the size and growth rate of predator populations.

Why are predator-prey interactions asymmetric at the individual level?

Because if the predator wins, the prey dies; if the prey escapes, the predator only misses a meal.

What kind of pressure does predation put on prey and predators?

Prey are pressured to avoid being eaten; predators are pressured to improve at finding and capturing prey.

What is the result of predator-prey interactions at the population level?

A co-evolutionary arms race, leading to adaptations in predators and prey.

What are owls classified as in terms of diet?

Medium to large birds of prey that are predators.

What do owls typically eat?

Insects, other birds, small mammals, and sometimes amphibians and reptiles.

Why are owls useful for studying food webs?

They eat prey whole and regurgitate indigestible parts in pellets, revealing dietary clues.

What is a gizzard and its function in owls?

A muscular organ that grinds food and traps bones, fur, and feathers of prey.

What is the difference between a crop and a gizzard in birds?

A crop stores food; owls lack a crop but use a gizzard to process food.

What is found in an owl pellet and what can it tell us?

Bones, exoskeletons, and fur; they reveal the prey diet and local hunting habits.

What does Marsupialia comprise?

Marsupial mammals.

What animal falls under Marsupialia? Provide the scientific and common name.

Didelpha virginiana (Virginia Opossum).

What are the dental characteristics of the Virginia Opossum?

Large canine teeth; lacks chisel-like incisors. Five pairs of upper incisors.

What are the general skull characteristics of the Virginia Opossum?

Small brain case, obvious sagittal crest, nasals expanded posteriorly; palatine vacuities present between molar tooth rows (Fig 17.1).

What are the morphological characteristics of the Virginia Opossum?

Each hind foot has an opposable thumb. Tail is thickened and prehensile. Female has a pouch in which the young are carried.

What are the behavioral characteristics of the Virginia Opossum?

Feigns death when threatened. Extremely omnivorous.

Is the Virginia Opossum native?

No, it was introduced near San Jose in 1910.

What comprises Eutheria?

Placental mammals.

What orders fall under Eutheria?

Artiodactyla, Carnivora, Eulipotyphla, Lagomorpha, and Rodentia.

What animals fall under order Artiodactyla?

Deer, cattle, pigs, sheep.

What are the characteristics of order Artiodactyla?

Even number of toes (2 or 4), the skull for one suborder, Ruminantia, has no upper incisors.

What animals fall under order Carnivora?

Dogs, wolves, foxes, cats, bears, otters, weasels.

What are the characteristics of order Carnivora?

The fourth premolar on the maxilla and first molar on the mandible are called carnassial teeth and adapted for shearing flesh in having a knife-like edge.

What animals fall under order Eulipotyphla?

Shrews, moles, hedgehogs.

What are the characteristics of order Eulipotyphla?

Sharp pointed teeth, molars have sharp cutting edges, no diastema (large space).

What animals fall under order Lagomorpha?

Hares, rabbits, pikas.

What are the characteristics of order Lagomorpha?

Two pairs of upper incisors, the second pair minute and directly behind the first; six pairs of upper cheek teeth; maxillary portion of rostrum fenestrated (Fig 17.6).

What animals fall under order Rodentia?

Squirrels, gophers, mice, voles.

What are the characteristics of order Rodentia?

Large space (diastema) separates upper and lower incisors from cheek teeth (premolars and molars), no canine teeth.

How is the length and width of the pellet written out on a label?

Specimen from owl pellet with dimensions xx mm L and xx mm W