2009 Week 2 Habitat
Using examples from your supplements and the chapters (Krebs & Davies 1993) about economic decisions (foraging), predator/prey (coevolution) and competition for resources, …..
Using examples from your supplements and the chapters (Krebs & Davies 1993) about economic decisions (foraging), predator/prey (coevolution) and competition for resources, …..
June 8th, 2009 at 9:45 am
…how have the models (hypotheses) tested by behavioral ecologists progressed from relatively simple (e.g. foraging decisions) to relatively more complex (e.g. foraging while avoiding predators and escalating conflict with competitors)? Is the logic of natural selection an underlying thread that is consistent throughout all these models, even as they increase in complexity?
June 12th, 2009 at 11:43 am
Throughout this week, the material has escalated from basic economic decisions to the co-evolution of a predator and its prey to finally the competition for resources. Essentially, we started with observing the behavior of a single individual and concluded by adding the components of competition. These three chapters have covered elements that are necessary to know when using the optimality model, such as currencies, constraints and the importance of testing hypotheses. Chapter three starts off with the model of the starlings and the decisions of what, when, how and where for foraging. It was hypothesized that the foraging behavior of the starling was a form of maximizing the net rate of the delivery of food. Chapter four had the model of underwing moths. The hypothesis that the forewings were a counter adaptation to the predation by decreasing detection was tested by Pietrewicz and Kamil (1981). They utilized a slideshow with pictures of moths, which was shown to birds to test their hypotheses. In Chapter five, exploitation was shown in the model of the sticklebacks distributing themselves according to the ratio of profitability of resources available.
Even as we increased complexity throughout the three chapters, the underlying thread was natural selection. For example, in the case of the underwing moths, if there was no variation among the pattern of the cryptic wings the birds would become accustomed to the pattern and the moths would therefore be more easily spotted.
June 12th, 2009 at 11:57 am
Natural selection is an underly thread that is consistent throughout all the tests from the text book, which have increased complexity. Take the bluegill sunfish example, when predators where not around, they enjoyed foraging mainly on benthos which is healthier but as soon as predators where introduced the bluegills adapated there foraging stragies to hiding in the reeds and near the banks rather than being out in the open feeding on benthos. Until the bluegills where a large size at least. they changed the foraging stragtey to help easy off predation stress where as this hypothesis is taken up a noch with the guppy example under chapter 4. the guppies where not only changing forage types due to the fact that some of what they eat affected there coloring which intern affected the noticability by predators. the brighter colors in some situations gave the guppies up to there predators while in different streams the brighter red colors actually helped then disappear from sight of there predators. The next example that i liked that further complexes the natural selection process is the interspecific competetion between the chaffinches and the great tits. these two birds in mainland settings shared various habitats but when confined to island habitats and limited space, they became competetors, so that this study spring from deciding forage preference then showed aggression in protecting ones terriortory then progressed to competetion among two different species. I do believe based on examples that natural selection is an underlying thread among all species that over time adapates different functions and stragies to a better way of life.
June 12th, 2009 at 4:07 pm
The models discussed in Krebs & Davies (1993) Chapters 3-5 have progressed from simple foraging strategies to more complex models using a building-block approach. We first discussed basic economic cost-benefits and the associated energy required and received through behavioral decisions. The example of starlings feeding on leatherjackets shows that starlings are designed through natural selection to maximize rate of food return to the young, thus maximizing differential fitness in that species. These models then progressed to foraging decisions and the dangers of predation, as illustrated in the decisions bluegills must make in the presence of predators (bass). Table 3.1 in Krebs & Davies (1993) summarized that many currencies (cost-benefits) and constraints (behavioral and physiological limitations) that species are attempting to maximize through natural selection; and the optimality model discussed in Chapter 2 allow researchers to test these currencies and constraints to determine the optimal and most efficient economic decisions. The presence of predators that determined economic decisions is impacted by the predator-prey relationships and adaptations/co-adaptations that species have developed through natural selection. Like the guppies discussed by Krebs & Davies (1993), trout have developed trade-offs between conspicuousness and crypsis. During most of the year, they have a molted pattern that reflects the streambed and make them difficult to spot from above by airborne predators. But this crypsis is shed during spawning time for bright crimson colors to attract mates and defend territories for mating. Thus natural selection has chosen for trout survival two distinct ways to ensure genotypes are passed; to survive until spawning time they need crypsis, and to successfully breed they require spawning colorations.
June 12th, 2009 at 5:26 pm
As the week two of this course has come and gone the foundation has been set and we continue to build upon that foundation. This week addressed the habitat aspects of behavioral ecology by delving into economic decisions, predator/prey interactions, and resource competition. The first aspect that peaked my interest was the study of the adaptation of cryptic forewing in moths. Kamil tested his hypotheses, of 1) Jays made more errors when the moths matched the background and 2) Jays learned search images, by the uses of a slideshow with moths in different backgrounds. Pietrewicz & Kamil (1981) This help to reinforce the differences in adaptations and story-telling. The next aspect the interested my greatly was the chaffinches and tits study. In this study Reed tested the conditional hypothesis by studying the chaffinch and tits completion. Reed (1981) On the mainland with abundant resources each species did not respond to the territorial songs to the other, yet on the island with limited resources each species responded to the others song with aggressive singing. Reed then removed the chaffinches from the island at which time the tits took over the territory. So due to the lack of recourses these species were forced to compete for resources that they would not normally compete over. Overall this week has increased my comfort level in this course and proves that I have a lot to learn.
June 12th, 2009 at 7:11 pm
In the case of individual economic decisions, I would say that there has been a clear progression from simple to more complex modeling approaches. Hypotheses begin as a comparative approach and progress into optimality models where they are supported, refined, or discarded. As more information is learned about cost/benefit analyses, constraints, and alternate currencies, scientists are able to better express new hypotheses and provide new insights through testing. Case in point, the starling example of foraging at the beginning of chapter 3; the hypothesis was that the starlings would have an optimal load size to maximize benefit and minimize cost. From that one hypothesis multiple optimality models can be developed, from how group information affects foraging patterns (J. J. Templeton, J. & Giraldeau, L. 1996) to how a flock will behave when confronted with a perceived predator (Devereux, C. 2006). I do believe that natural selection is an underlying theme throughout these cited optimality models and the ones listed in the textbook, and the fact that they are more complex lends support the idea of natural selection taking place.
Templeton, J. & Giraldeau, L. 1996. Vicarious sampling: the use of personal and public information by starlings foraging in a simple patchy environment. Behavioral Ecology. 38, 105-114.
Devereux, C., Whittinghama, M., Fernández-Juricicc, E., Vickeryd, J. & Krebs, J. 2006. Predator detection and avoidance by starlings under differing scenarios of predation risk. Behavioral Ecology. 17, 303-309.
June 12th, 2009 at 7:14 pm
Editors note: the article entitled “Vicarious sampling: the use of personal and public information by starlings foraging in a simple patchy environment” came from the Behavioral Ecology and Sociobiology journal, not Behavioral Ecology.
June 12th, 2009 at 7:56 pm
If you were to survey one acre of old growth forest in Oregon and ask the question, “what is a solution to the problem of foraging for survival in this environment dominated by Douglas-fir trees and a temperate costal climate?” you would be surrounded by many examples. You might observe life being sustained by foraging for small mammals in the trees, invertebrates in the soil, herbs growing on the forest floor or insects from the air. These survival solutions are also known as behavioral adaptations. The extensive fauna biodiversity present in that one acre, everything from simple worms and invertebrates, to snakes and frogs on up to birds and mammals, are all historical representatives of the variation in possible solutions (behavioral adaptations) to the challenge of foraging. If you more closely examine the spotted owl’s foraging preference you would see that it preys on flying squirrels and tree voles (Forseman and Meslow 1984). To understand from a scientific perspective, why the spotted owl forages as it does, hypothesis testing would be needed to evaluate its behavioral adaptations. The comparative approach could be used to understand how that behavior converged or diverged from its avian ancestors. This method could be used to qualitatively test the reasons the spotted owl forages for flying squirrels instead field mice like another species of owl. Hypothetically, if you were to find that the spotted owl captured its prey from the trees instead of the ground like the other owl species did, they you could use the optimality approach to understand the costs and benefits of this type of foraging. The optimality method provides a quantitative assessment of the degree of differential fitness associated with this behavior. The next questions to explore could be “how did the spotted owl and its prey coevolved?” and “how does the spotted owl compete for this limited resource?” The answers to each one of these questions have their own optimal fitness value, but the individual species must be capable of reacting with a behavioral response appropriate to survive all of its life challenges. When you consider that there are behavioral adaptations for foraging, mating, reproduction, competing, evading/predating and so on, the complexity compounds. For this reason, it is important to consider all of the confounding variables and the possibility of colinearity when testing hypothesis. The equation of natural selection (NS = V+H+D+P) becomes similar to a massive polynomial equation because of all the possible variation in the solution to life. It is no wonder that millions of animal species inhabit the earth (May 1988).
Forseman, E.D, Meslow, E.C., and Wight, H.M. 1984. Distribution and Biology of the Spotted Owl in Oregon. Wildlife Monographs 87: 3-64.
May RM. 1988. How many species are there on earth? Science. Vol. 241: 441-1449.
June 12th, 2009 at 7:57 pm
Walter, I agree with your viewpoint on the starling example. When reading chapter three of Krebs & Davis’s book, the hypothesis about the starlings becomes more complex.
I concur that the models tested by behavior ecologist have progressed from simple models to more complex. Starlings were first tested based on foraging decisions, and next the models measured currencies. After these considerations constraints of the models were determined. The starlings were tested on the tradeoffs of costs and benefits on page 49 of Krebs and Davis. The starlings disproved the energy model and accepted the time hypothesis. Natural selection is consistent throughout the levels of complexion within the hypothesis, and variation is an underlying thread that plays a role in the simplistic models as well as the complex.
June 15th, 2009 at 7:44 am
from an email: “I have discovered a fascinating and educational web site, called
http://www.ted.com.
One great video you will all enjoy is on the intelligence of the American Crow, please check out this particular page. I will forever ban using the term “bird brains” in a derogatory fashion! It’s a 10 minute video and will take a little time to download before playing.
http://www.ted.com/talks/lang/eng/joshua_klein_on_the_intelligence_of_crows.html
June 15th, 2009 at 7:51 am
Any thoughts about how the co-evolution of wolves and crows/ravens may have influenced intelligence as a behavioral trait adapted to a fluctuating environment?
September 9th, 2009 at 10:36 pm
Intelligence can be seen in many different ways. Crows dropping dog food into water to soften it up is a good example of intelligence. Is this intelligence inherited or learned? Social learning from watching others is usually a sufficient way to survive. Watching others do something that helped the ones before survive is usually a safe bet. But one individual had to branch out and try something new, like that first crow that figured out it could soften dog food with water. My best example of an individual learning by trial and error is a zoo study with chimps. I do not remember which zoo did the study but they were attempting to measure the problem solving skills of the chimps. The zoo designed an elevated platform with clear plastic tube in the center. This tube ran down a few feet to the ground and was open at the top, level with the platform. They proceeded to drop an apple to the bottom of the tube, just out of reach for the biggest chimp. The chimp tried every way he could think of to get that apple. He pushed on the bottom of the tube. He stuck his arm down the tube from the top but the apple was just out of reach. Finally he gave up trying to get the apple. He was sitting on the platform, obviously thinking about how to get that apple when a baby chimp ambled up next to him. The old chimp looking at the little chimp, then looked back at the tube, and back at the young one, then back to the tube. Then all of a sudden, he grabbed the little chimp by the hind leg and stuck him head first into the tube. The little monkey was startled and calmed down in a couple of minutes. After calming down, he noticed the apple and grabbed it. As soon as he grabbed the apple, the big chimp jerked him back out and grabbed the apple the little chimp was holding. After that, whenever the big chimp found an apple at the bottom of the tbe, he would run grab the little chimp to get his apple for him. I always thought this to be an interesting example of intelligence.