fleeing predation lecture - pnb2xc3

Crown eagle video clip

• Hunting of vervet monkeys of all sizes in East Africa

• Predator-prey race: monkeys stay away from exposed tree tops —> eagles fly among trees —> monkeys have a special eagle alarm call and attempt to drop to dense bushes

• Parental care: 4 months in the nest, 9 months to independence

Balancing feeding and antipredatory behaviour in ants

• Ants could choose between two patches containing liquid ant diet of different concentrations

• The high conc patch was either safe or had a predator

• Ants preferred the safer less rewarding patch as long

• It was not much worse (as low as 8 times worse or 12%) and

• the predator remained active (4 vs 25h: predator’s attack rate declined over time)

Horse racing

• 0.3% of horse weight would cause a ½ body length speed reduction at the finish

The optimal amount of fat in birds

• Birds vary their fat reserves depedning on expected benefits and costs

• More fat when food is less certain

• Less fat when predation risk is higher

Hatching decisions of red eye frog embryos

• Rapid response to the snake attack

• Embryos rely on vibration cues

• Frequency, duration and spacing of vibration events

• The eggs are laid on leaves above the water

• Hatched tadpoles drop to the water

• The leaves are associated with terrestrial predators (snakes and wasps), the water has aquatic predators (shrimp and fish)

• Peak hatching of undisturbed eggs is at 7 days

• Early hatching is associated with higher predation on the tadpoles in the water

Is hatching age affected by predation?

• Experiment: let experimental treatments of eggs to be attacked by snakes at the ages of 5-6 days and monitor hatching

• Eggs respond to predation on neighbouring eggs hatching earlier

• The eggs avoided almost certain predation by dropping into dangerous water, where younger tadpoles have a higher probability of predation than older tadpoles

Parasitism

• Less eye catching than predation but a major cause of mortality in all animals including humans

• For historic reasons we term tiny parasites such as bacteria and viruses disease

Death from parasites

• 40 million people in the world have aids

• 42 milion people have died from aids since 1981

• Flu kills 30k people a year in the USA

• SARS, avian flu, COVID-19

Malaria

• Malaria may have killed half of all the people that ever lived

• In 2021, there were 247 million cases of malaria and 619k people died, most of them children under the age of five. More than 95% of malaria os found in Africa

• Cheap vaccine approved in 2023

Parasite avoidance in tree frogs

• Snails are intermediate hosts of a trematode parasite (protozoa)

• Experiment comparing egg laying in sites with

• No snails, low and high parasite infection rates, low and high snail densities

• As expected from evolutionary considerations, animals attempt to minimize the risks of predation and parasitism