Mammalogy Exam 2 PDF

Sexual Selection and Mating Systems 1. Understand anisogamy and how it influences sexual selection ultimately the mating systems of mammals Ansiogamy: difference in gamete size (describes all mammals) - Females have large eggs that are energetically expensive and limited, and males have sm...

Sexual Selection and Mating Systems 1. Understand anisogamy and how it influences sexual selection ultimately the mating systems of mammals Ansiogamy: difference in gamete size (describes all mammals) - Females have large eggs that are energetically expensive and limited, and males have small sperm that is energetically cheap and readily available, causing asymmetry in parental investment with females having more investment. Males often compete for females because eggs are a limiting resource, all females breed but only certain males. Sperm Competition (Intrasexual selection) 1) Reduce the chances for a later male Methods: - Mate guarding (following around) - Copulatory plug (secretion deposited in vagina to plug the reproductive tract shut, allows time for this sperm to fertilize egg) 2) Reduce the chances for the previous male - Dilution (a lot of secondary semen) 2. Understand how female choice influences male phenotypes (i.e., sexual selection) How do females determine male quality? - Morphological characteristics like color, size, or ornamentation - Behavioral characteristics like dominance, aggression - Symmetry: indicates the ability to maintain developmental homeostasis in the presence of environmental variation and stress Sexual Dimorphism - Pressure of anisogamy and sexual selection often leads to sexual dimorphism which differentiates morphology between males and females (typically size) Bateman Gradient - The slope of regression between mating success and reproductive output/success - Sex with the steepest slope (usually males) is the most likely to experience the strongest selection pressure on sexual dimorphic characteristics that enhance success 3. Differentiate between the two types of sexual selection Intersexual selection: one sex choose certain mates of the other sex based on certain traits they possess Intrasexual selection: individuals of one sex compete among themselves for an individual of the other sex (male-male competition) 4. Compare and contrast the primary mating systems employed by mammals Monogamy Exclusive mating relationship between one male and one female Polygyny One male mates with multiple females Polyandry One female associates with multiple males, may copulate with one or more males Promiscuity No prolonged associations between sexes, multiple copulations by at least one sex *Polygamy describes 90% of mammals, only 10% of mammals practice monogamy. Types of Polygyny Resource Defense Polygyny - Males defend a territory - Polygynous behavior because resources females need are clumped spatially Female Defense Polygyny - Males defend natural aggregations of females Male Dominance Polygyny - Arenas where males aggregate and compete for space where females are known to aggregate - Common with ungulates Scramble Polygyny - One male attempts to secure as many female mates in an area as possible through a competitive searching approach 5. Understand how sociality and environment influence the mating system employed by a Species Social Behavior and Communication 1. Understand the Sociality Spectrum Sociality: group living, willingness to tolerate conspecifics to some degree (not 100% antagonistic) - Most mammals fall between asocial and eusocial 2. Understand Why Mammals Live in Groups Describe Benefits Reduced predation - Encounter dilution (group encountering predator does not increase with size)  - Many eyes hypothesis (more time foraging, less time looking for predators) - Group defense (more = less likely to be predated) Social learning/cultural transmission of information - Where to find food - How to capture food Describe Costs - Competition for resources - Increased disease/parasite transmission 3. Understand How Mammals Communicate - Exchange of information between sender and receiver via a signal - Signal: behavioral/morphological structure that sender uses to transmit information to the receiver Why communicate? - Group spacing and coordination - Recognize species, individuals, mate, kin - Reproductive status - Social status or dominance - Predator alarm - Hunting - Soliciting care a. Describe Modes of Communication Olfactory: scent/pheromones can be detected at any time of day and lasts after individual leaves - Pheromones: produced by specialized glands, found in feces/urine, received through jacobson’s organ - Best for nocturnal species (lack of light) and relatively asocial animals that do not have frequent physical contact Flehmen response: - Retraction of upper lip to bring air into mouth and contact with vomeronasal organ Sound - Can change rapidly, communicate a lot of information quickly - Can travel long distances - Different frequencies for different situations or environments - Good for both nocturnal and diurnal species - Ex: prarie dog different calls Vision - Visual communication via displays, signal involves structure or ritualized behavior with visual component (movement, coloration, posturing) - Displays often precede direct aggression and reduce energy expenditure/potential for injury, often accompanied by auditory or olfactory signals  - Can always locate signaler precisely in space and time - Diurnal species Flagging behavior - Distract predator from other members of group - Warn other members - Signal to predator it has been detected - Ex: white tail deer Spatial Ecology 1. Describe different types of space use Nomadism: undefended, constantly searching for unpredictable fleeting resources, nothing to defend Home range: lightly defended, resources predictably distributed across space and time (can predict when/where to defend) Home range with core area: moderately defended, resources predictably distributed across space and time (can predict when/where to defend) Territory: highly defended, resources predictably distributed across space and time (can predict when/where to defend) 2. What is a home-range? - Area traversed by individual during normal activities such as foraging, mating, caring for young - Home range size is indicative of space needed to survive and reproduce Why do animals establish home-ranges? - Efficiency in finding food, cover, mates - Safety (familiarity) How is a home-range established? - Memory of resource quality and distribution makes movement more calculated and efficient, individual will continue to return until a home range is established 3. What is habitat selection? - Pattern of use of a habitat type relative to availability/abundance of that habitat type Describe why animals select habitat - Habitat selection increases fitness - Individuals physiology (heat/water tolerance) and cognitive ability influencing their determination of pattern of habitat use - Habitat selection: process of using environmental information to guide patterns of habitat use - Shaped by natural selection and learning to maximize survival/reproduction - Habitat selection is directly linked to home range Ideal Free Distribution: - Theoretical way individuals in a population distribute themselves to minimize competition and maximize fitness, individuals at high density areas will occupy more different habitats Describe how habitat selection behaviors arise - Natural selection likely shapes an animals ability to make decisions on habitat selection, however this covers a broad ability to select habitat and does not exist under a narrow set of conditions (plasticity matters), otherwise species would not be able to distribute themselves under high densities 4. Why do animals disperse from their natal range? - Majorly to facilitate gene flow within/between populations - Inbreeding depression: inbreeding reduces reproductive success and survival of offspring compared to unrelated parents - Outbreeding depression: breeding between members of different populations with different local adaptations can yield less fit offspring - Intraspecific competition: resources can only support a finite number of individuals Types of Dispersal - Dispersal: movement away from home range to create new home range - Natal dispersal: movement away from area mom raises young to independent (not connected) home range - Philopatry: post-natal dispersal home range near natal home range, typically overlapping with natal home range 5. What is seasonal migration? - Round trip movements between two distinct seasonal ranges Why do animals migrate? - Resource tracking (vegetation growth, salmon migration) - Escape harsh temperatures - Escape parasites Consequences: - Tracking enhances fitness (access to quality/abundant food, escape parasites/predators, escape weather conditions) - Migratory populations are larger than sedentary populations - Impacts ecosystem, transports some elements from one seasonal range to another (seeds, parasites, diseases) b. How do animals navigate between seasonal ranges? - Spatial memory and cognitive maps of range - Social learning and cultural transmission Population Ecology 1. Differential between different types of population growth Life history: how organisms grow, survive, and reproduce over time Life history trait: any variable/trait that influences population dynamics (not including natural history traits), litter size, age at reproductive maturity, neonate survival, juvenile survival Natural history: ecology, how individuals interact with each other and the environment, behavior, diet, habitat requirements, CAN include life history traits What is the difference between natural history and life history? Natural history describes how individuals interact with each other and their environment. Life history describes a trait that influences population dynamics. Life history traits are not natural history traits, and include variables such as age specific survival, reproductive maturity, or litter size. Natural history characteristics cover behavior, habitat and diet preferences, and can include life history traits. 3. Understand Ecological and Nutritional Carrying Capacity Population Growth Logistic growth/density dependent growth: Describes population growth that is dependent on density. As density of a population increases, life history traits decrease at a predictable rate towards the carrying capacity. Considered a conservative life history strategy because adult females trade reproductive success for survival and chance of being able to reproduce in the future. In management, populations can be maximally harvested at half the carrying capacity. What is the difference between ecological and nutritional carrying capacity? Ecological carrying capacity is the number of individuals an area can support without causing unsustainable changes to the ecosystem. Nutritional carrying capacity is the number of individuals an area can support based on habitat and climatic conditions, or the total available nutritional energy. As populations approach the carrying capacity, limited resources mean there is low body fat and muscle/protein reserves. This coupled with annual variation in plant production or other environmental factors cause populations to respond to density independent factors like weather. What does it mean by nutritional carrying capacity? Carrying capacity is dependent on resources available for intraspecific competition. The maximum number of animals that nutritional resources can support. Why is nutritional carrying capacity a better concept than classic ecological carrying capacity? - classic/ecological carrying capacity considers the overall habitat space and resources available when determining the limit of population size, however nutritional carrying capacity provides a more direct link between availability and quality of food and seasonal/density independent variables that impact population size Exponential/density independent growth: A population growth pattern where the population grows faster as it gets larger Nutritional Buffer Hypothesis: Recruitment becomes more selective in unfavorable weather conditions as population approaches nutritional carrying capacity 2. Understand density-dependence and density independence 4. Understand what causes population cycles Population cycles are generally imperfect in most cases. Population cycles are most commonly linked to factors such as climate, variation in forage quality dependent on season Predator-prey interactions: prey are limited by predation, and remain in a declined state even after predator numbers decline due to chronic stress Community Ecology 1. Understand Niches & Competition Community ecology: study of species interactions and their influence on composition and abundance of different species living in the same place Horizontal interaction: species within a single trophic level Vertical interaction: species at different trophic levels (ex predator-prey, plant-herbivore) Ecological Niche: all environmental (biotic and abiotic) conditions needed to maintain stable or positive growth rate (lambda greater than or equal to 1) *if populations are not stable or are declining, those environmental conditions would not be considered part of the niche Fundamental Niche: the environmental conditions needed for a population to maintain a stable or positive growth rate in the absence of competitors, predators, parasites/diseases Realized Niche: the environmental conditions needed for a population to maintain a stable or positive growth rate coinciding with competitors, predators, parasites/diseases (the reality) Understand niche partitioning Competition: the use of resources by two or more species that reduces their fitness or population growth rate w/d: if width/distance between niche center increases, this suggests that there is more competition. When distance is large, competition is low (small/large number), but when width is large, competition is high (large number over small) Graph A: - strong competition that influenced these species to partition resources so each could coexist Graph B:  - Species have large niche overlap which could potentially lead to niche partitioning OR if resources are not limiting each species can use these resources without reducing their fitness Describe competitive exclusion - States that two species cannot coexist if they occupy the same niche - Coexistence theory: interactions between the same species are more competitive than interactions between different species (so in the graph, species a would be more competitive with its own species than species b), so graph A is common and follows competitive exclusion (two species cannot coexist in the same niche) - In most cases, if two species coexist there is niche differentiation - It is much easier to determine how species interactions determine niche partitioning, but difficult to determine if competition is occurring Competitive release: a species expanding its realized niche to occupy more of fundamental niche when there is less competition or a lack of a competing species Describe how to study competition Removal experiments allow scientists to determine if species experience competitive release when removing a potential competitor by studying the changes in their fitness/demographic Understand niche plasticity Niches become broader (TNW increases) as competition becomes stronger. Animals are more picky about resources (use less, better quality resources) when competition is lower, but develop a broader niche in high competition. ***Niches are plastic, and change over time - Broader niches mean that interactions are more likely to occur, alters interactions and competition coefficients Community Ecology Main Points - Niche partitioning/overlap is the key component to horizontal interactions and species coexistence - The degree of competition between two species requires removal or addition experiments because niche overlap does not say much about competition - Niches are plastic and change depending on resource limitation and competition