DOCSLIB.ORG

A Practical Technique for Measuring the Behavior of Foraging Animals

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Practical Technique for Measuring the Behavior of Foraging Animals g k sTHow A PractIcal Technique for )D Do Measuring the Behavior of It _ . It Foraging hnlmalS RosemaryJ. Smith Joel S. Brown Animal behavior is well suited for havioral questions that can be readily ness (survivaland reproduction).If so, illustrating ecological and evolution- addressed gives students the opportu- an animal should leave a patch when ary principles. For ecology projects or nity to suggest their own hypotheses its benefits of continued feeding in the labs, animal behavior has a number of and experiments.The projectsempha- patch no longer exceed its cost of feed- advantages:It is inherently interesting size the methodology of a scientist ing in the patch. The formal frame- Downloaded from http://online.ucpress.edu/abt/article-pdf/53/4/236/45243/4449276.pdf by guest on 01 October 2021 to most students, it can be observed, it and, we hope, the excitement that work behind the assertion in the pre- is flexible and it can change quickly. accompanies creative thinking and vious sentence is called Optimal Unfortunately, meaningful observa- novel results. Foraging Theory (see Stephens & tions of behavior tend to be time- Krebs 1986). consuming and difficultto analyze. To We begin by elaborating a rule for overcome this handicap, we introduce Rationale when an animal should leave a patch an indirect procedure that uses the and then discuss how this rule can be foraging behavior of animals at exper- "Talking" to animals requires a common language, and feeding be- used to reveal aspects of that animal's imental food patches to address ques- ecology. An example from our own tions in animal behavior. The data are havior can provide just such a lan- guage. Mixing food into a substrate work illustratesthis rule. We provided the food left behind by the animals. kangaroo rats living in the Sonoran Such creates a food patch and provides a data are quantitative and easily Desert of Arizona with shallow alumi- analyzed using a variety of technique for "asking" foragers how descriptive num pans (45 x 45 x 2.5 cm) filled with or inferential statistics. The experi- they perceive their environment. The a known amount of millet seed (3 g) mental procedure encourages stu- food patches are like a survey distrib- dents to ask questions relevant to how uted to the animalsbeing investigated. that has been mixed into 3 1 of sifted environmentalfactors such as climate, The animals fill out the survey by dirt. Kangaroorats foraged enthusias- vegetation structure and predation digging for and harvesting food from tically in these food patches. As more risk influence animals'foraging behav- the tray's substrate and then sign and more seeds are eaten, the large ior. When several species are included these trays with footprints, body amount of dirt in the patch makes it within the study, interspecific differ- marks and other telltale disturbances increasingly difficult for the kangaroo ences in behavior provide an easy and of the substrate. The amount of food rats to find the seeds that remain. relevant introduction to questions of left in the patch contains the answer to Therefore, the benefit of remaining in niche separation and species coexis- the survey. the patch declines. At some density of tence. The following approach to feeding seeds the cost of looking for the next Because it uses food left by animals behavior represents evolutionaryecol- seed exceeds the benefit derived from in feeding patches, the technique does ogy. From an ecological perspective, harvesting and consuming that seed. not require hours of observation, han- two universal properties of life in- At this criticalseed density the kanga- dling of animals or expensive equip- clude: roo rat should leave the patch. If it ment. Because feeding is central to all 1. Births and deaths continues to forage past this density, it animals regardless of environment, 2. The need for energy and nutri- forages at a loss (costs exceed bene- studies can be conducted on school ents to maintainhomeostasis and fits). If it quits early, it forfeits the food campuses using urban birds (spar- life functions that it could have profitablygained. rows, doves, pigeons, starlings) or An animal should leave a food patch small mammals (squirrels, mice and From an evolutionary perspective, when its benefits equal its costs (see rats). The cost/benefit theory behind these two properties of life encourage Brown 1988 for a formal treatment of the technique is intuitive and accessi- animals to have feeding behaviorsthat the theory). To apply this foraging ble to students. The breadth of be- allow them to acquire food in an effi- theory, the animal must experience a cient manner. declining rate of return from spending Feeding animals make decisions time in the food patch, and the animal about where to feed (habitatselection, must experience both benefits and Rosemary J. Smith teaches in the de- MacArthur & Pianka 1966), what to costs from exploiting the patch. The partment of ecology and evolutionary feed on (diet choice, Pulliam1974) and benefit to biology at the Universityof Arizona,Tuc- the forager is its rate of son, AZ85721. Joel S. Brownteaches in when to quit an area and move to harvest of food times (H) considered the department of biological sciences another location (patch use, Charnov in terms of energy or nutrient intake. at the Universityof Illinois,Box 4348, 1976). We assume that natural selec- The costs of spending time in a food Chicago, IL60680. tion has favored those animals whose patch include energetic costs (E) of feeding decisions maximize their fit- searchingfor and handling food items, 236 THEAMERICAN BIOLOGY TEACHER, VOLUME 53, NO. 4, APRIL1991 walk. And finally, if you knew there VARYINGFORAGING COSTS was another full jar on the shelf, or [ENERGETIC,MISSED OPPORTUNITY OR PREDATIONI that you were missing out on a great TV show (high missed opportunity costs), again you would leave more peanut butter in the jar. m The amount of peanut butter left in the jar, the GUD, is a clearreflection of D z 4- your perceptionof these three types of costs. Refer back to the equation and note that if any two costs are held constant, any differencesin GUDs be- o 3 tween experimentaltreatments will in- dicate the effect of the variationin the third cost (see Figure 1 for summary). 2 z Methods Using GUDs to Study Feeding Downloaded from http://online.ucpress.edu/abt/article-pdf/53/4/236/45243/4449276.pdf by guest on 01 October 2021 o 1 Costs & Opportunities The model predicts that two identi- > Low HIGH cal feeding patches placed side by side within the same habitat should have Figure 1. An illustration of how giving up density of peanut butter might vary the same GUD. This is because both with experimental conditions. The LOW giving up density relative to HIGH trays have the same substrate and indicates a lower energetic, missed opportunity or predation cost of extracting food items (controls for H) are subject peanut butter from a jar. to the same microclimaticconditions (controlsfor E), are equally exposed to potential dangers (controls for P), are equally situated for alternative activi- ties (controls for M) and are available A Useful Analogy of the Rule for to the same animals (differentanimals risk of predation (P) and the missed in their of the Leaving Patches may vary perceptions opportunity cost (M) of not engaging food, energetic costs of foraging, pre- in alternativefitness-enhancing activi- We have found that the following dation risk and opportunities pro- ties such as mating, defending a terri- human example of the patch-leaving vided by alternative activities). The tory or-exploiting a richer food patch. rule is useful because it provides stu- above prediction allows for controlled The patch-leaving rule can then be dents with a mental image of the way manipulations of the model's compo- written as: GUDs change when the cost compo- nents (H, E, P and M). The effect of nents are manipulated. Imagine an any one of the components on the H = E + P + M almost empty peanut butterjar (this is GUD can be tested by holding the the resource patch). As you remove other components constant. In what This rule provides the model for peanut butter from the jar it becomes follows it is important to remember investigating foraging behavior. An more and more difficultto get the next that higher GUDs mean more food is spoonful out (this demonstrates a de- left in the patch, hence the animals animal should leave a food patch clining rate of return). According to either perceived higher costs or lower when the harvest rate from the patch the rule, you will quit removing pea- benefits from harvesting the patch. no longer exceeds the sum of the en- nut butter when the benefit (the har- Consider an investigation of factors ergetic, predation and missed oppor- vest rate) just equals the sum of the that may influence harvest rates. Plac- tunity costs of foraging. In reality, it is costs (energetic,predation and missed ing food patches side by side within difficult to measure H and even more opportunity). The amount of peanut the same habitat can control for ener- difficult to measure H, E, P and M in butter left in the jar will be your GUD. getic costs, predation risk and missed terms of their fitness consequences, Now, what happens when one of opportunity costs. By varying food which is their true common currency. the costs is varied while the others are types, food size or substrate, it is pos- Fortunately, the density of food left held constant? When it is cold and sible to test for their effects on H. behind in a patch when an animal more energy is required to scrape out Larger amounts of substrate or more quits foraging is a good surrogate for the last bit of peanut butter (higher difficult substrates should increase H.
Load more

Recommended publications
  • Foraging Modes of Carnivorous Plants Aaron M
    Israel Journal of Ecology & Evolution, 2020 http://dx.doi.org/10.1163/22244662-20191066 Foraging modes of carnivorous plants Aaron M. Ellison* Harvard Forest, Harvard University, 324 North Main Street, Petersham, Massachusetts, 01366, USA Abstract Carnivorous plants are pure sit-and-wait predators: they remain rooted to a single location and depend on the abundance and movement of their prey to obtain nutrients required for growth and reproduction. Yet carnivorous plants exhibit phenotypically plastic responses to prey availability that parallel those of non-carnivorous plants to changes in light levels or soil-nutrient concentrations. The latter have been considered to be foraging behaviors, but the former have not. Here, I review aspects of foraging theory that can be profitably applied to carnivorous plants considered as sit-and-wait predators. A discussion of different strategies by which carnivorous plants attract, capture, kill, and digest prey, and subsequently acquire nutrients from them suggests that optimal foraging theory can be applied to carnivorous plants as easily as it has been applied to animals. Carnivorous plants can vary their production, placement, and types of traps; switch between capturing nutrients from leaf-derived traps and roots; temporarily activate traps in response to external cues; or cease trap production altogether. Future research on foraging strategies by carnivorous plants will yield new insights into the physiology and ecology of what Darwin called “the most wonderful plants in the world”. At the same time, inclusion of carnivorous plants into models of animal foraging behavior could lead to the development of a more general and taxonomically inclusive foraging theory.
    [Show full text]
  • Foraging : an Ecology Model of Consumer Behaviour?
    This is a repository copy of Foraging : an ecology model of consumer behaviour?. White Rose Research Online URL for this paper: https://eprints.whiterose.ac.uk/122432/ Version: Accepted Version Article: Wells, VK orcid.org/0000-0003-1253-7297 (2012) Foraging : an ecology model of consumer behaviour? Marketing Theory. pp. 117-136. ISSN 1741-301X https://doi.org/10.1177/1470593112441562 Reuse Items deposited in White Rose Research Online are protected by copyright, with all rights reserved unless indicated otherwise. They may be downloaded and/or printed for private study, or other acts as permitted by national copyright laws. The publisher or other rights holders may allow further reproduction and re-use of the full text version. This is indicated by the licence information on the White Rose Research Online record for the item. Takedown If you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing [email protected] including the URL of the record and the reason for the withdrawal request. [email protected] https://eprints.whiterose.ac.uk/ Foraging: an ecology model of consumer behavior? Victoria.K.Wells* Durham Business School, UK First Submission June 2010 Revision One December 2010 Revision Two August 2011 Accepted for Publication: September 2011 * Address for correspondence: Dr Victoria Wells (née James), Durham Business School, Durham University, Mill Hill Lane, Durham, DH1 3LB & Queen’s Campus, University Boulevard, Thornaby, Stockton-on-Tees, TS17 6BH, Telephone: +44 (0)191 334 0472, E-mail: [email protected] I would like to thank Tony Ellson for his guidance and Gordon Foxall for his helpful comments during the development and writing of this paper.
    [Show full text]
  • Water Stress Inhibits Plant Photosynthesis by Decreasing
    letters to nature data on a variety of animals. The original foraging data on bees Acknowledgements (Fig. 3a) were collected by recording the landing sites of individual We thank V. Afanasyev, N. Dokholyan, I. P. Fittipaldi, P.Ch. Ivanov, U. Laino, L. S. Lucena, bees15. We find that, when the nectar concentration is low, the flight- E. G. Murphy, P. A. Prince, M. F. Shlesinger, B. D. Stosic and P.Trunfio for discussions, and length distribution decays as in equation (1), with m < 2 (Fig. 3b). CNPq, NSF and NIH for financial support. (The exponent m is not affected by short flights.) We also find the Correspondence should be addressed to G.M.V. (e-mail: gandhi@fis.ufal.br). value m < 2 for the foraging-time distribution of the wandering albatross6 (Fig. 3b, inset) and deer (Fig. 3c, d) in both wild and fenced areas16 (foraging times and lengths are assumed to be ................................................................. proportional). The value 2 # m # 2:5 found for amoebas4 is also consistent with the predicted Le´vy-flight motion. Water stress inhibits plant The above theoretical arguments and numerical simulations suggest that m < 2 is the optimal value for a search in any dimen- photosynthesis by decreasing sion. This is analogous to the behaviour of random walks whose mean-square displacement is proportional to the number of steps in coupling factor and ATP any dimension17. Furthermore, equations (4) and (5) describe the W. Tezara*, V. J. Mitchell†, S. D. Driscoll† & D. W. Lawlor† correct scaling properties even in the presence of short-range correlations in the directions and lengths of the flights.
    [Show full text]
  • Predation Risk and Feeding Site Preferences in Winter Foraging Birds
    Eastern Illinois University The Keep Masters Theses Student Theses & Publications 1992 Predation Risk and Feeding Site Preferences in Winter Foraging Birds Yen-min Kuo This research is a product of the graduate program in Zoology at Eastern Illinois University. Find out more about the program. Recommended Citation Kuo, Yen-min, "Predation Risk and Feeding Site Preferences in Winter Foraging Birds" (1992). Masters Theses. 2199. https://thekeep.eiu.edu/theses/2199 This is brought to you for free and open access by the Student Theses & Publications at The Keep. It has been accepted for inclusion in Masters Theses by an authorized administrator of The Keep. For more information, please contact [email protected]. THESIS REPRODUCTION CERTIFICATE TO: Graduate Degree Car1dichi.tes who have written formal theses. SUBJECT: Permission to reproduce theses. The University Library is receiving a number of requests from other institutions asking permission to reproduce dissertations for inclusion in their library holdings. Although no copyright laws are involved~ we feel that professional courtesy demands that permission be obtained from the author before we ~llow theses to be copied. Please sign one of the following statements: Booth Library o! Eastern Illinois University has my permission to lend my thesis tq a reputable college or university for the purpose of copying it for inclul!lion in that institution's library or research holdings. Date I respectfully request Booth Library of Eastern Illinois University not allow my thesis be reproduced because ~~~~~~-~~~~~~~ Date Author m Predaton risk and feeding site preferences in winter foraging oirds (Tllll) BY Yen-min Kuo THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF Master of Science in Zoology IN TH£ GRADUATE SCHOOL, EASTERN ILLINOIS UNIVfRSITY CHARLESTON, ILLINOIS 1992 YEAR I HEREBY R£COMMEND THIS THESIS BE ACCEPTED AS FULFILLING THIS PART or THE GRADUATE DEGREE CITED ABOVE 2f vov.
    [Show full text]
  • Photosynthetic Pigments Estimate Diet Quality in Forage and Feces of Elk (Cervus Elaphus) D
    51 ARTICLE Photosynthetic pigments estimate diet quality in forage and feces of elk (Cervus elaphus) D. Christianson and S. Creel Abstract: Understanding the nutritional dynamics of herbivores living in highly seasonal landscapes remains a central chal- lenge in foraging ecology with few tools available for describing variation in selection for dormant versus growing vegetation. Here, we tested whether the concentrations of photosynthetic pigments (chlorophylls and carotenoids) in forage and feces of elk (Cervus elaphus L., 1785) were correlated with other commonly used indices of forage quality (digestibility, energy content, neutral detergent fiber (NDF), and nitrogen content) and diet quality (fecal nitrogen, fecal NDF, and botanical composition of the diet). Photosynthetic pigment concentrations were strongly correlated with nitrogen content, gross energy, digestibility, and NDF of elk forages, particularly in spring. Winter and spring variation in fecal pigments and fecal nitrogen was explained with nearly identical linear models estimating the effects of season, sex, and day-of-spring, although models of fecal pigments were 2 consistently a better fit (r adjusted = 0.379–0.904) and estimated effect sizes more precisely than models of fecal nitrogen 2 (r adjusted = 0.247–0.773). A positive correlation with forage digestibility, nutrient concentration, and (or) botanical composition of the diet implies fecal photosynthetic pigments may be a sensitive and informative descriptor of diet selection in free-ranging herbivores. Key words: carotenoid, chlorophyll, diet selection, digestibility, energy, foraging behavior, nitrogen, phenology, photosynthesis, primary productivity. Résumé : La compréhension de la dynamique nutritive des herbivores vivant dans des paysages très saisonniers demeure un des défis centraux de l’écologie de l’alimentation, peu d’outils étant disponibles pour décrire les variations du choix de plantes dormantes ou en croissances.
    [Show full text]
  • Interpreting Temporal Variation in Omnivore Foraging Ecology Via
    Functional Ecology 2009 doi: 10.1111/j.1365-2435.2009.01553.x InterpretingBlackwell Publishing Ltd temporal variation in omnivore foraging ecology via stable isotope modelling Carolyn M. Kurle*† Ecology and Evolutionary Biology Department, University of California, 100 Shaffer Road, Santa Cruz, CA 95060, USA Summary 1. The use of stable carbon (C) and nitrogen (N) isotopes (δ15N and δ13C, respectively) to delineate trophic patterns in wild animals is common in ecology. Their utility as a tool for interpreting temporal change in diet due to seasonality, migration, climate change or species invasion depends upon an understanding of the rates at which stable isotopes incorporate from diet into animal tissues. To best determine the foraging habits of invasive rats on island ecosystems and to illuminate the interpretation of wild omnivore diets in general, I investigated isotope incorporation rates of C and N in fur, liver, kidney, muscle, serum and red blood cells (RBC) from captive rats raised on a diet with low δ15N and δ13C values and switched to a diet with higher δ15N and δ13C values. 2. I used the reaction progress variable method (RPVM), a linear fitting procedure, to estimate whether a single or multiple compartment model best described isotope turnover in each tissue. Small sample Akaike Information criterion (AICc) model comparison analysis indicated that 1 compartment nonlinear models best described isotope incorporation rates for liver, RBC, muscle, and fur, whereas 2 compartment nonlinear models were best for serum and kidney. 3. I compared isotope incorporation rates using the RPVM versus nonlinear models. There were no differences in estimated isotope retention times between the model types for serum and kidney (except for N turnover in kidney from females).
    [Show full text]
  • Foraging Ecology of a Winter Bird Community in Southeastern Georgia
    Georgia Southern University Digital Commons@Georgia Southern Electronic Theses and Dissertations Graduate Studies, Jack N. Averitt College of Fall 2018 Foraging Ecology of a Winter Bird Community in Southeastern Georgia Rachel E. Mowbray Follow this and additional works at: https://digitalcommons.georgiasouthern.edu/etd Part of the Behavior and Ethology Commons, and the Population Biology Commons Recommended Citation Mowbray, Rachel E., "Foraging Ecology of a Winter Bird Community in Southeastern Georgia" (2018). Electronic Theses and Dissertations. 1861. https://digitalcommons.georgiasouthern.edu/etd/1861 This thesis (open access) is brought to you for free and open access by the Graduate Studies, Jack N. Averitt College of at Digital Commons@Georgia Southern. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of Digital Commons@Georgia Southern. For more information, please contact [email protected]. FORAGING ECOLOGY OF A WINTER BIRD COMMUNITY IN SOUTHEASTERN GEORGIA by RACHEL MOWBRAY (Under the Direction of C. Ray Chandler) ABSTRACT Classical views on community structure emphasized deterministic processes and the importance of competition in shaping communities. However, the processes responsible for shaping avian communities remain controversial. Attempts to understand distributions and abundances of species are complicated by the fact that birds are highly mobile. Many species migrate biannually between summer breeding grounds and wintering grounds. The goal of this study was to test four hypotheses that attempt to explain how migratory species integrate into resident assemblages of birds (Empty-Niche Hypothesis, Competitive-Exclusion Hypothesis, Niche-Partitioning Hypothesis, and Generalist-Migrant Hypothesis). I collected data on birds foraging during the winter of 2017-2018 in Magnolia Springs State Park, Jenkins County, Georgia, U.S.A.
    [Show full text]
  • Nocturnal and Diurnal Foraging Behaviour of Brown Bears (Ursus Arctos) on a Salmon Stream in Coastal British Columbia
    Color profile: Disabled Composite Default screen 1317 Nocturnal and diurnal foraging behaviour of brown bears (Ursus arctos) on a salmon stream in coastal British Columbia D.R. Klinka and T.E. Reimchen Abstract: Brown bears (Ursus arctos) have been reported to be primarily diurnal throughout their range in North America. Recent studies of black bears during salmon migration indicate high levels of nocturnal foraging with high capture efficiencies during darkness. We investigated the extent of nocturnal foraging by brown bears during a salmon spawning migration at Knight Inlet in coastal British Columbia, using night-vision goggles. Adult brown bears were observed foraging equally during daylight and darkness, while adult females with cubs, as well as subadults, were most prevalent during daylight and twilight but uncommon during darkness. We observed a marginal trend of increased cap- ture efficiency with reduced light levels (day, 20%; night, 36%) that was probably due to the reduced evasive behaviour of the salmon. Capture rates averaged 3.9 fish/h and differed among photic regimes (daylight, 2.1 fish/h; twilight, 4.3 fish/h; darkness, 8.3 fish/h). These results indicate that brown bears are highly successful during nocturnal foraging and exploit this period during spawning migration to maximize their consumption rates of an ephemeral resource. Résumé : Les ours bruns (Ursus arctos) sont généralement reconnus comme des animaux à alimentation surtout diurne dans toute leur aire de répartition. Les résultats d’études récentes sur les ours noirs durant la migration des saumons indiquent qu’ils font une quête de nourriture intense pendant la nuit et que l’efficacité de leurs captures est élevée à l’obscurité.
    [Show full text]
  • Seabird Foraging Ecology
    2636 SEABIRD FORAGING ECOLOGY Ballance L.T., D.G. Ainley, and G.L. Hunt, Jr. 2001. Seabird Foraging Ecology. Pages 2636-2644 in: J.H. Steele, S.A. Thorpe and K.K. Turekian (eds.) Encyclopedia of Ocean Sciences, vol. 5. Academic Press, London. SEABIRD FORAGING ECOLOGY L. T. Balance, NOAA-NMFS, La Jolla, CA, USA Introduction D. G. Ainley, H.T. Harvey & Associates, San Jose, CA, USA Though bound to the land for reproduction, most G. L. Hunt, Jr., University of California, Irvine, seabirds spend 90% of their life at sea where they CA, USA forage over hundreds to thousands of kilometers in a matter of days, or dive to depths from the surface ^ Copyright 2001 Academic Press to several hundred meters. Although many details of doi:10.1006/rwos.2001.0233 seabird reproductive biology have been successfully SEABIRD FORAGING ECOLOGY 2637 elucidated, much of their life at sea remains a mesoscales (100}1000km, e.g. associations with mystery owing to logistical constraints placed on warm- or cold-core rings within current systems). research at sea. Even so, we now know a consider- The question of why species associate with different able amount about seabird foraging ecology in water types has not been adequately resolved. At terms of foraging habitat, behavior, and strategy, as issue are questions of whether a seabird responds well as the ways in which seabirds associate with or directly to habitat features that differ with water partition prey resources. mass (and may affect, for instance, thermoregula- tion), or directly to prey, assumed to change with Foraging Habitat water mass or current system.
    [Show full text]
  • Fifty Years of Food and Foraging in Moose: Lessons in Ecology from a Model Herbivore
    ALCES VOL. 46, 2010 SHIPLEY - MOOSE AS A MODEL HERBIVORE FIFTY YEARS OF FOOD AND FORAGING IN MOOSE: LESSONS IN ECOLOGY FROM A MODEL HERBIVORE Lisa A. Shipley Department of Natural Resource Sciences, Washington State University, Pullman, Washington 99164-6410, USA ABSTRACT: For more than half a century, biologists have intensively studied food habits and forag- ing behavior of moose (Alces alces) across their circumpolar range. This focus stems, in part, from the economic, recreational, and ecosystem values of moose, and because they are relatively easy to observe. As a result of this research effort and the relatively simple and intact ecosystems in which they often reside, moose have emerged as a model herbivore through which many key ecological ques- tions have been examined. First, dietary specialization has traditionally been defined solely based on a narrow, realized diet (e.g., obtaining >60% of its diet from 1 plant genus). This definition has not been particularly useful in understanding herbivore adaptations because >99% of mammalian herbi- vores are thus classified as generalists. Although moose consume a variety of browses across their range, many populations consume 50-99% of their diets from 1 genus (e.g., Salix). Like obligatory herbivores, moose have demonstrated adaptations to the chemistry and morphology of their nearly monospecific diets, which precludes them from eating large amounts of grass and many forbs. New classifications for dietary niche suggest that moose fit on the continuum between facultative special- ists and facultative generalists. Second, moose have been the subject of early and influential models predicting foraging behavior based on the tradeoffs between quality and quantity in plants.
    [Show full text]
  • Rangeland Herbivores Learn to Forage in a World Where the Only Constant Is Change Larry D
    ARIZONA COOPERATIVE E TENSION AZ1518 July 2010 Rangeland Herbivores Learn to Forage in a World Where the Only Constant is Change Larry D. Howery, Frederick D. Provenza, Beth Burritt Introduction When we go to the grocery store it is a fairly easy task to select and purchase nutritious meals. A readily available, predictable food supply is conveniently organized and displayed in the aisles. The nutritional composition of most foods is clearly labeled so you can immediately know what nutrients (and perhaps, toxins) you will be consuming. In contrast, rangeland animals live in a world where nutrients and toxins are constantly changing across space and time. For example, there may be 10’s to 100’s of plant species ROVENZA growing on a single acre, and each plant can differ widely F. D. P F. BY in the kinds and amounts of nutrients and toxins it offers to free-ranging herbivores. Even at the level of the individual HOTO plant, plant parts vary in their concentration of nutrients and P toxins. Leaves, stems, and flowers, all differ in the kinds Photo 1. Mother can have a profound influence on her offspring’s dietary and amounts of nutrients and toxins they contain. Nutrient preferences and toxin content of the same plant species can also vary depending on where it grows (in the sun vs. shade, on a wet Exposure to foods with mother at an early age vs. dry site, on a fertile vs. infertile site, etc.). Mother Nature has long-term effects on diet selection can also drastically alter foraging environments as a result of We have all heard the old adage “mother knows best.” natural disasters like floods, fires, or droughts.
    [Show full text]
  • American Beaver Foraging Ecology: Predation Avoidance, Diet, and Forage Availability
    AMERICAN BEAVER FORAGING ECOLOGY: PREDATION AVOIDANCE, DIET, AND FORAGE AVAILABILITY By William J. Severud THESIS Submitted to Northern Michigan University In partial fulfillment of the requirements For the degree of MASTER OF SCIENCE Graduate Studies Office 2011 SIGNATURE APPROVAL FORM This thesis by William J. Severud is recommended for approval by the student‟s thesis committee in the Department of Biology and by the Dean of Graduate Studies. __________________________________________________________________ Committee Chair: Dr. John G. Bruggink Date __________________________________________________________________ First Reader: Dr. Jerrold L. Belant Date __________________________________________________________________ Second Reader: Dr. Steve K. Windels Date __________________________________________________________________ Third Reader: Dr. Alan J. Rebertus Date __________________________________________________________________ Department Head: Dr. Patrick W. Brown Date __________________________________________________________________ Associate Provost and Dean of Graduate Studies, Grants, Research, and Continuing Education: Dr. Terrance Seethoff Date OLSON LIBRARY NORTHERN MICHIGAN UNIVERSITY THESIS DATA FORM In order to catalog your thesis properly and enter a record in the OCLC international bibliographic data base, Olson Library must have the following requested information to distinguish you from others with the same or similar names and to provide appropriate subject access for other researchers. NAME: Severud William James
    [Show full text]