NRS305 Final Exam 2024./2025 100% VERIFIED ANSWERS, Exams of Nursing

Download NRS305 Final Exam 2024./2025 100% VERIFIED ANSWERS and more Exams Nursing in PDF only on Docsity! NRS305 Final Exam 2024./2025 100% VERIFIED ANSWERS Population regulation is a term that emerged from the earliest decades of the wildlife ecology discipline. What does population regulation mean? Keeping populations from getting out of control. Naturally, populations are regulated in the wild by K because they never grow exponentially. How did the examples of whooping cranes, bighorn sheep in the Western US, Vancouver marmots, white sharks, and New England cottontails illustrate the different ways in which population regulation is important in wildlife management and conservation? Whooping cranes have low chick survival rates. Bighorn sheep populations are struggling, how do you boost populations? Predator regulation? Vancouver marmots extremely low population, facing regular predation rates. New England cottontail reintroduction programs threatened by predation. For many issues in wildlife ecology, the primary focus is on top-down influences (effects of the predators on prey). This is especially the case with news stories in the popular press, in which vertebrates that consume other vertebrates get more attention than organisms at lower trophic levels. What is responsible for the disproportionately strong focus on predators and predation compared to other factors that regulate populations? Predators dominate top of food chains, but are populations at lower levels kept below K by consumption from above? There is top down bias, because we are predators. Predators pose conservation and management problems, but lack of predators can also be a big problem (anti-predator adaptations). Evolutionary importance of predators is obvious. In the case of white-tailed deer in non-farmland-dominated regions of Wisconsin, a decline in deer populations coincided with the growth of the wolf population in the state; this could understandably lead some people to think that deer populations were being regulated by wolf predation. What were some alternative explanations for the apparently negative relationship between deer and wolf densities in non-farmland-dominated regions of Wisconsin? Deer population boom and bust was unrelated to wolves. -Increased hunting from humans -Increased antler collection -A more violent winter -Food webs What is it about real systems in nature that contradict the oftentimes simplistic view of the density or behavior of a predator being the most important factor in explaining the density or distribution of a prey species? Also, what variables would you need to measure (and what data would you need to collect) to test the hypothesis that predation is an important regulator of a prey population? -immigration, emigration, carrying capacity -food chains part of much larger food web, many predators rely on the same prey -Stochastic events -Distribution of a prey species due to the distribution of their food In the simplest model of the predator density being regulated by prey density, the growth of the predator population is constrained only by its own death rate and which variables are associated with the prey? (On the exam you will be given the equation with one of the variables blacked out) dP/dt = acRP - dP P: # predators R: # prey a: efficiency of conversion of food to growth (how well prey converts to new predator) c: constant for efficiency of predation (how well predators deplete prey) d: constant for death rate of predators This simple model (for the predator) assumes what about the predator's feeding behavior and food requirements? What is it about real predators in nature that makes this assumption unrealistic? Efficiency is how well predators kill prey (kill rate). A small amount of M&Ms has no chance of survival, where M&Ms in a big bowl have a larger chance of survival. Why would we expect predator efficiency to change as prey availability (i.e., the size of the prey population) increases? Would it decrease or increase, and why? Why might we expect the shape of this change (the relationship between predator efficiency and prey density) to not be linear? Predator efficiency would increase as prey population increases because the more prey there is the easier it is to catch and kill them Prey might be good at hiding, or predators might be good hunters. Resembles type II if efficiency increases as the prey gets more abundant but eventually plateaus when the predators have reached max amounts of eating ability Resembles type III when the predators still have trouble catching prey until density increases and eventually plateaus Under what circumstances might predation efficiency decline with decreasing prey densities? Think about behavioral characteristics of real predators and ecological characteristics of real environments. When there are less prey, it is less likely for any one predator to catch them, especially with increased competition due to a decrease in food. What is a search image, and what role might it play in the functional relationship between predator and prey populations? Search image takes time and high prey abundance. Increased familiarity for something the more you encounter it. Less common prey is harder to hunt, so when numbers are lower there is less of chance that the prey will develop a search image/it will take longer. Is immigration or emigration implicitly included in the numerical or functional responses above? How might immigration/emigration influence the relationship between predator and prey populations? Emigration. Both influence as wolves can't find them easily as their population in that area declines. How might territorial behavior of the predator influence the relationship between predator and prey populations? If a predator defends a certain area means there are less predators in the area. Might mean lower predation rates and lower satiation number. This would lead to a higher prey population in this territory if it was being modeled by the models above that only take into account one predator eating the prey. What is it about Isle Royale that makes it a seemingly ideal system for studying the relative importance of top-down and bottom-up factors in regulating prey populations? It is a mostly isolated island with an N that can be counted for every population, makes studying effects easier. How and when did the moose colonize the island? Colonized ~1910 by swimming. How and when did the wolves colonize the island? Colonized in 1948, crossed ice when the water froze. Other than wolves, what factors influence moose populations? Availability of vegetation. Other than moose, what factors influence wolf populations? Population fluctuation from returning to main land after water freezes over. To what extent (if at all) does the wolf-moose relationship on Isle Royale resemble the famous lynx-hare cycle? Specialized predator-prey interactions directly influence each others populations. Once the predators peak and prey is over hunted, the predators decline and allow prey to peak. For the moose à resource relationship, what are rmax, K, a, h, and c; and how do they affect the relationship? What ecological or physiological realities do these variables incorporate into the models? For the wolf à moose à resource relationship (a tri-trophic model), the equations are somewhat different from those above. For this relationship what are a, b, d, and e (and the corresponding variables for wolves A, B, D, and E), and how do they affect the relationship? What ecological or physiological realities do these variables incorporate into the models? When field or lab-based estimates are plugged in for these variables and the models are run, what is the nature of the predicted dynamics? What happens when a density-dependent term is added to the model for wolves? What ecological reality does this density-dependent term represent? To what extent (if any) do the model projections resemble the real moose-wolf relationship that has been documented over the last several decades? What are your thoughts on the potential utility of LV models for predicting wolf-moose dynamics on Isle Royale? What role do stochastic/unpredictable events play in determining the eventual dynamics? Give some examples of some of such events that have occurred on Isle Royale over the years. What is the concept of the "landscape of fear" (you can look it up—there is a lot of popular press and scientific literature on it), and how might it factor into the Isle Royale system. What is your opinion on the recent plan (of the US Park Service) to reintroduce wolves to Isle Royale? Back up your statement with as many facts and concepts as you can; you should also thoughtfully consider the idea of "naturalness" and the role of humans as visitors and manipulators of environments. How might changes in migratory behavior or patterns of migration influence predator efficiency? Lower predation rate for elks that adapted to migrate How might increased vigilance of prey influence predator efficiency? Prey being more cautious of predators decreases predator efficiency How might increased vigilance of prey influence the feeding patterns (when and where they feed) of prey? There was a release of population of beavers in Gallant National Park just north of Yellowstone Mech (2012); In what way are the effects of water table level, beaver densities, and willow recovery confounded? (confounding occurs when your ability to infer cause-and-effect from the relationship between x and y is thwarted by the effect of a third variable (z) on x and/or y.) Wolves may not have been the factor in willow recovery but beavers were; they raised the water table Mech (2012); What evidence did the author point to in casting doubt on the role of the wolf reintroduction on the decline of elk in the Northern Range? Human harvest, harsh winter, drought, other predators Mech (2012); What other factors (e.g., climate variation, and changes in populations of other species of herbivores and carnivores) in the Greater Yellowstone Ecosystem must be considered before ascribing the 'chief savior' status to the wolf? Worse winter conditions, drought, human harvest, increased grizzly bear numbers, long-term reduction in moose, increased growing season of willow Mech (2012); Why did the author warn against scientists 'sanctifying' the wolf? Biases may be associated with wolves, they could only be seen as having positive effects while there could also be negative ones Mech (2012); Why did the author suggest that results from the putative trophic cascade in Yellowstone, even if true, would not be particularly useful to wildlife conservation and management in most of the US? Different researchers use different methods in different locations and come to different conclusions Trophic cascades may occur locally Effects and interactions among uncontrolled factors are poorly understood Most of N. America is incomparable (lacks big predators and vast, protected landscapes) Describe the two-year cycle of the black-legged tick A female lays ~1500 eggs in May, all of which are pathogen free. In August larvae attach and feed on anything, particularly white footed mice, which is where they pick up the pathogens. Larvae feed for 3-4 days and then drop off the host. For several months the larvae molt and grow into their adult forms. Once they have reached adulthood they feed on mammals and transmit the pathogens, and then reproduce and repeat the cycle. Black-legged tick _Ixodes scapularis_ Lyme-causing spirochete _Borrelia burgdorferi_ White-footed mouse _Peromyscus leucopus_ Until a few years ago, white-tailed deer were considered the most important factor in the increase/spread of Lyme disease. Why? They were previously thought to be the primary vector due to high populations. What factors are thought to be responsible for the increase in deer populations from the 1970s through the last decade? Reforestation and restorations of deer populations, less over hunting of deers. The potential contributions of white-tailed deer to Lyme disease join what other publicly- unfavorable aspects of high deer populations? Deer cause heavy crop loss, as well as major road accidents. What is the evidence against deer populations being the primary contributor to the recent increase in Lyme disease? That white footed mice are the primary vector for lyme. Deer populations have begun to level off despite the increasing lyme cases. WFM predators are in decline What evidence would one expect to see if deer populations were the primary contributor to the recent increase in Lyme disease? Increasing populations where they have instead leveled off. What role might coyotes have played in the recent spread of Lyme, according to Levi et al. (2012)? There's an increase in coyotes but a decrease in red fox, a primary consumer of white-footed mice, the most prominent vector for lyme Describe the relationships involved in the putative effects of coyotes on Lyme disease. In your answer include the concepts of the trophic cascade and mesopredator release. Coyotes competed with foxes for food, which reduced the number of foxes, which in turn reduced the number of small mammals killed, increasing the spread of Lyme. What evidence suggests that the commonness of coyotes in New England is a relatively recent phenomenon? Coyotes had been hunted out because they are viewed as a public nuisance. They are slowly making their way back with the increase in deer population. How are the past and current distributions of gray wolves related (apparently) to the recent spread of coyotes? When gray wolves were extirpated, it allowed the coyotes to expand their territory with less competition What is it about the feeding behavior of the red fox that makes it such a potentially strong regulatory agent in controlling the populations of vertebrate hosts of tick nymphs? Red fox prey primarily on small mammals, which are the primary vector of lyme. Less small animals means less vectors for tick nymphs to pick up lyme. The data compiled by Levi et al. (2012) on red fox and coyote population came from where (from what kinds of observations)? Citizen surveys If you wanted to experimentally test the mesopredator release theory (Levi et al. (2012) how would you do this? What variables would you manipulate or control for? fox population indices, live mice trapping, tick surveys