Study Guides (247,941)
Canada (121,182)
York University (10,191)
Biology (573)
BIOL 3170 (7)


8 Pages
Unlock Document

BIOL 3170
Alexander Mills

Lecture 10 Predation- Non-Lethal effects Predator Prey Red Fox Roe Deer Hopilias Guppies (Poecilia) & Killifish (Rivulus) Coyotes & Lynx Snowshoe Hare Non-lethal: means that it does not cause death About the Case 1. Roe Deer (common in Europe) are caused to die due to predation by the Red foxes especially the young. Small body size makes the young vulnerable to Red foxes. Mothers hide their fawns (young) visiting them 3-7 times a day to feed them. Mothers however do not stay with the young. Method of study: 14 years and 216 fawns were radio collared to maintain their survival and cause of death. Results: Less vulnerability as the young grows older shown by the graph. Predation rate declines when they are older. Predation rate was 42% when the deer were young due to predation by the fox. About the Case 2 (Fraiser & Gilliam 1992) Guppies (Poecilia) & Killifishor jumping guabine (Rivulus) both live in a forest streams on the hillsides. Their pop is broken into subpop and they occupy different pools separated by riffles. Hoplias is a predator which indirectly effects these two species in terms of emigrations, death rate, reproduction etc. The study was done to find out about the -emigration & death rate -egg production by Rivulus -growth rate of Rivulus -Habitat preferences Method of study Emigration/ Death and Habitat (1) Predator was introduced to an upstream pool and monitored after 24 hours (2) Prey density was controlled by emptying and restocking pools and then introducing two individual Hoplias. Reproduction Effects (3)Artificial outdoor stream in New York measured the number of eggs laid on artificial substrates in different parts of the stream. Growth Rates (4)Measured and weighed the individual prey then exposed them to artificial streams with and without the predator . Then after the end of experiment they were re-measured and weighed again. Results: Emigration/Death (Emigration away from presence of predators) - individuals emigrated downstream -The death rate in 24 hour % varied by species and size class Reproduction ( Egg production decreases) 1 -Egg production (#s of eggs) by Rivulus was much lower (50% lower) -Mostly egg production was low where predators were present Growth Rate (decreases) -Adult Rivulus stopped growing the presence of predator (TRADE OFF) negative energy budget since they were losing mass, - Smaller females produce smaller eggs since their size effects their reproductive system. However, their smaller body may allow them to move and forage more effectively in the riffles preventing predators. Habitats (Shift to worst places with less food for survival) -They shifted from deeper pools to upstream areas where there is less food, and less water but to maintain their survival rates (an example of TRADE OFF). ** Juveniles for both species did not show any significant** About the Case 3 (Sherif et all 2009) Snowshoe-hares are very common, can be known as the fast food of Boreal forests. Two key predators are Coyotes and Lynxes. They undergo population cycles every 8-10 years. Predator populations peak shortly after the hare population. For e.g. in Hares it peaked in 2006 and in predators it peaked in 2007. Female reproductive rate becomes lower when the predator rates are higher. Sherif et all predicted the rates. -Predicted the non-lethal effects of predators on the prey - Proposed that increased hormone cortisol reduces the reproductive success -High levels of cortisol helps you cope with fear but it should be low otherwise you can expire at young age. TRADE OFF. Method of study/design: (1) Measure female cortisol levels and reproductive rate, along with predator numbers over the course of a population cycle (2) Experimentally manipulate predator (such as trained dogs) to stress the captive hares to determine the direct effects on cortisol levels and reproduction. Results: Stressed females had SMALLER OFFSPRING / females exposed to predators were very stressed -CAPTIVEAND WILD-The higher the number of cortisol, the higher the females are stressed and small the offspring/and reduced body mass. -There was NOT statistical difference WITHIN each litter, but BETWEEN each litter WITHIN: perhaps because this population cycle was weak BETWEEN: prob due to better food and lower predation risk The 1 litter in the wild pop was bad, HIGH CORTISOL, low offspring, smaller offspring, body size etc nd The 2 litter in wild pop was better , FEMALES WERE LESS STRESSEDALMOST BY 52% ; litter size increased ; offspring mass increased; foot size increased Reproduction becomes better in 2 litter (TRADE OFF) Lecture 11 Metamorphosis: Biological process by which an animal physical develops The deadly effects of NON-lethal predators 3 major players include (1) Dog-tailed White face(prey) (2) Green Darner(predator) (3) Blue Gills sunfish (predator) -Dog-tailed white face reproduce via wheel mating and oviposting (laying eggs) in water. The larvae is called nymph. During the metamorphosis the nymph jumps out of the water and flies away. Experiment was done to measure the morphological stress in the presence of the two predators. Divided into 2 Experiments -Experiment (1) was based on effects of predator exposure on larval mortality at HIGH PREDATOR DENSITIES The two prey sources were from the fishless and fishponds The 3 treatments involved (1)|Bluegills Present (2) Green Darner (3) No Predators -Experiment (2) was based on the effects of predator exposure on larval mortality , metamorphic success, morphological changes at LOW PREDATOR DENSITY The two prey sources were from the fishless and fishponds The 3 treatments involved (1)Single Blue gill fish present (2) No predators (in a cage) Results: Experiment 1: Despite DIRECT CONSUMPTION, higher survival rates were present in the NON-PREDATOR treatment Experiment 2: Also higher survival rates were present where there was no fish Also the rate of Emergence (when they come out of the shell and fly out) was 10% higher where there was no FISH Conclusion: Mortality effects predators presence; metamorphosis BUT NO MORPHOLOGICAL EFFECTS (such as smaller size) Lecture 12 Induced Plant Defenses: Wild Tobacco plant producing Nicotine No herbivore (losing situation since there is less seed production using more energy to defend against nothing) Herbivory (high and low ) winning situation because even though there is less seed production compared to plants with no herbivory; however the plant is defending against the herbivores) InducedAnimal Defenses: Mayfly with long tail filaments (with Fish / Fishless environment) -concept of phenotypic plasticity/norm of reaction: One may or may not go about producing the defense since it comes with the cost. ----------------------------------------------------------------------------------------------------------------------------------------------- Lecture 13 Numerical Response: More predators move into an area in response to high prey density. Functional Response: When there is an increase in prey numbers, each predator eats more individuals per predator (TYPE 3) Buzz Holing: expert in predator prey relationship; came up with numerical & functional response ideas Gyrfalcons (predator) and Ptarmigan (prey) - Biggest in the world; found in Canada and they prey heavily upon the ptarmigan. Both population vary from year to year.A rapid increase in ptarmigan population increases the gyrfalcons(numerical response) but then there is a decline (SEE GRAPH) since there is less predators feeding per prey ( functional response). Conclusion: They appear to accelerate the decline; ------------------------------------------------------------------------------------------------------------------------------------------------- Introduced mammals: Red foxes were introduced inAustralia (non-native) species. Astudy was done to find out if red foxes caused the decline of native small mammals specifically Bush rats. Methods: 2 removal sites ; 2 control sites Results: Bush rats reproductive rate and survival rate is not affected . There was no significant results. 3 Conclusion: Other predators may have compensated for the Red fox, bush rat population was maybe food-limited rather than predator limited. Doomed Surplus: The over produced population will die anyway; if not by one predator than by another. --------------------------------------------------------------------------------------------------------------------------------------------------- Predator Removal: White-footed mice and chipmunks are predators of the song bird nests.Astudy done did a removal experiment with both predators. Chipmunk removal had impact but mice had a huge impact on the population. Methods: Used artificial bird nests; plasticine eggs to record teeth marks to determine if chipmunk OR mice was there to eat the eggs. Results: Mouse removal caused a decline in the mortality rate; Chipmunks and other predators did not have much impact. Conclusion: High mouse density deplete sources for other predators and therefore mice are the dominant predators.(SEE GRAPH) Lecture 14 Parasites and Changes in Reproductive traits: Blue-black grass quit & parasite (reduction in feathers leads to lower nested success) -Honest indicators= system used by females to find males Test involved 4 groups = Tails shortened; natural tails(uncut) ; tails cut & regaled (same length) ; artificially glued tails Results= Group 4 had higher success ( artificially long tails preferred by females ; higher nested success) ------------------------------------------------------------------------------------------------------------------------------------------------ Parasites and Host behaviour changes: Killifish (host); (Euhaplorchis Californisis trematode (Parasite) ; Heron (bird ,predator of the killifish) Test involved 2 experiments: parasitized & unparasitized fish in both indoor and outdoor pool nd 2 experiment involved (exposure to herons vs no herons) Results= Parasitized fish show conspicuous(shimmying, flashing) behaviours to be eaten to complete the life cycle to enter birds Life cycle of parasite= Snail Fish (killifish) Heron (bird) ------------------------------------------------------------------------------------------------------------------------------------------------ Parasite and Population Regulation: Red Grouse populations are regulated by Nematode -Study shows that females produce low brood (offspring) with high parasitic levels Tests= Females were fitted with radio transmitters and half were treated with drug resistant to parasite Results: Females (treated with drug) had a higher reproductive success and higher survivorship (REFER to Graph) Females not treated with drug suffered higher predation by Gyrfalcons and also lower reproductive success Conclusion= Parasite regulates the population oscillations(cycles) in Red Grouse population; suppressing the parasite will suppress the oscillations . Population crashes in Red grouse are driven by parasites. Another example is the Moose and deer population, In mid 20 century deer #s increased due to changes in forest (forest fires etc) and moose populations decreased. Reason was that moose suffer from a parasite that does not effect the deer. Moose survive in mature forests, and deer in immature so moose population was high again due to changes in the forest structures. Lecture 15 Parasite and Population Regulation: 3 major players ;Arabdiposis (plant host) ; Phytoplasma bacteria (parasite) ; Leafhopper (spreads the disease) - The Arabdiposis plant when effected by Phytoplasma bacteria changes the plant morphology and causes witches brooms, which interfere with plants reproductive traits, longevity(long life). The leaf hopper moves the phytoplasma from plant to plant and they a
More Less

Related notes for BIOL 3170

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.