predator-prey relationships

Question 1

species reintroduction, Yellowstone national park

Answer 1

• reintroduced wolves in 1950s to control prey populations that were fluctuating and damaging the environment
• success in managing prey species as the area was large enough to sustain a population of large carnivores

Question 2

Haley wood, Cambridgeshire

Answer 2

• ancient woodland
• suffered damage from deer species
• controlled populations using culling and fencing, area is too small to sustain a population of predators

Question 3

Hudson Bay, Canada

Answer 3

• large fur trade, kept a record of hides shot, sold and traded
• relationship between number of hides and population size of predator and prey species
• reflection of past population size

Question 4

wildlife’s 10 year cycle, Canada

Answer 4

• snowshoe hare numbers follow availability of woody browse
• lynx follows, 9-10 year oscillating cycle
• other herbivores follow same cycle as they are predated on more when hare number are low
• possibly follows 10 year solar cycle

Question 5

Lotka and Volterra

Answer 5

• hypothesised that there was a simple oscillating relationship between prey and predator number/ density
• as prey population increases, predator population increases after a lag

Question 6

Gause (1930s), experiments with protozoans

Answer 6

• predator prey interactions between Paramecium caudatum (prey) and Didinium nasutum (predator)
• contradicts simple Lotka, Volterra model
• populations of both crashed
• introduced a refuge, prey population sustained in short term, predator population collapsed
• introduced immigration every 3rd day, both populations sustained over a longer period of time

Question 7

Huffaker’s orange universe (1950s)

Answer 7

• using phytophagous mite totetranchyus (prey) and typhiodromus mite (predator) on mouldy oranges
• introduced environmental heterogeneity to the system by adding rubber balls and vaseline barriers that the predator couldn’t cross and introduced new individuals
• 252 oranges needed to sustain population
• system sustained for 70 days

Question 8

what does a sustainable predator-prey system rely on

Answer 8

• environmental heterogeneity
• immigration
• emigration

Question 9

diversity in prey species

Answer 9

• increases success
• tawny owl numbers maintain a constancy of abundance despite fluctuations in wood mice and bank voles as they do not solely rely on that species
• species that are able to adapt to occupy niches are more successful e.g. Badgers eating rabbits in Spain nature reserve

Question 10

predator responses to an increase in prey population density

Answer 10

• numerical response, density increases, population booms, e.g. Sorex shrew in response to increase in sawfly numbers
• functional response, density increases by a small amount, species consumes more of the prey e.g. Blarina shrew in response to an increase in sawfly numbers, number of cocoons found opened in a specific way increases

Question 11

avoidance of predation

Answer 11

• camouflage e.g. twig caterpillar
• chemical defense e.g. skunk
• warning colouration advertising noxiousness e.g. monarch butterfly
• mimicry
• behaviour, cooperation in social groups

Question 12

Batesian mimicry

Answer 12

• species evolved to look like noxious prey

Question 13

Mullerian mimicry

Answer 13

• two or more noxious species sharing common predators evolve to look like each other to their mutual benefit

Question 14

predator strategies

Answer 14

• cooperation, forming social groups
• using lures e.g. angler fish