Papers by Michael Rosenzweig
The Bulletin of the Ecological Society of America, 2021
Bulletin of the Ecological Society of America, 0(0) Article e01884 Ecologist William (Bill) M. Sc... more Bulletin of the Ecological Society of America, 0(0) Article e01884 Ecologist William (Bill) M. Schaffer died on 16 January 2021, in Tucson, Arizona, USA. He is survived by his wife, Tanya, and his children, Michael and Margaret. Bill was best known in ecology for his work on the theory of life history evolution and on nonlinear dynamics, but his contributions were much broader and his influence on the field substantial (Fig. 1). Bill was an iconoclast. His work was brilliantly original, and he always aimed to ask fundamental questions. Most of his work was theoretical. While he used his excellent computational and coding skills (starting with Fortran) to solve difficult mathematical problems, he was skeptical of complex and elaborate computer models, always aiming to explain phenomena in terms of basic principles. He was excited about ideas and would express his enthusiasm to great effect. He had tremendous respect for rigorous and original thinking. Bill was the quintessential embodiment of the scholar who does not suffer fools gladly (at least those he considered fools), and he did not keep those opinions to himself. Yet, he could be lavishly kind and supportive as well. He was a difficult taskmaster, graduating only seven Ph.D. students, but those students became influential academic scholars themselves. No matter what he was doing, Bill Schaffer always worked toward 100% success. When he made Peking duck, he had to have all the authentic ingredients, all the techniques, and two days of spare time. (The result was pure beauty.) Bill loved trains, particularly old-fashioned ones pulled by steam locomotives, and constructed an elegant and extensive model train layout to celebrate them. Bill Schaffer was simply a polymath with a drive to excel in whatever challenges he set upon. While Bill lived in the west for his entire professional life and wore the cowboy boots to prove it, he had deep roots in the east. Born in Elizabeth, New Jersey, on 11 May 1945, he attended the Hackley School, in New York State, where he graduated as Valedictorian. As an undergraduate at Yale, Bill quickly became deeply immersed in research. He wrote a paper in the undergrad Yale Scientific Magazine on Charles Lyell and the origin of species (Schaffer 1965). He also wrote about male-male combat and morphology in the Caprinidae (sheep and goats) alone and with his advisor (Schaffer 1968, Reed and Schaffer 1972a, Schaffer and Reed 1972b). He earned his Bachelor's degree Magna cum laude with High Honors in Biology and was a member of Phi Beta Kappa.
Evolutionary Ecology Research, 2017
Aim: Test the hypothesis that predators influence the fitness of their prey by taking prey indivi... more Aim: Test the hypothesis that predators influence the fitness of their prey by taking prey individuals disproportionately in poorer condition. Questions: How do wild, herbivorous animals taken by predators in nature differ from those that survive? Organisms: Wild prey – Saiga tatarica (an antelope) and Lepus europaeus (brown hare). The predator – trained hunting dogs (sighthounds). Methods: We compared the prey taken by sighthounds in the field to those shot by human hunters. We conducted pathological, anatomical, and microbiological studies and compared the results for prey taken by sighthounds with prey taken by human hunters. We used GPS technology to track, second by second, the speed and direction of hounds that were hunting. To determine the concentration of microorganisms on their skin, we studied animals killed by human hunters as well as by hounds. Finally, we studied the reaction of the hounds to olfactory stimuli of bacterial origin. Results: The hunting success of the ho...
Evolutionary Ecology Research, 2018
Background: In a series of aviary experiments, we showed that little egrets (Egretta garzetta, th... more Background: In a series of aviary experiments, we showed that little egrets (Egretta garzetta, the predators) and common goldfish (Carassius auratus, their prey) play a behavioural game in which the egrets adjust the timing of their predatory visits to experimental pools, and the fish adjust their exposure to predation by moving between a safe habitat that lacks food and a risky habitat that contains food. But we did not determine whether they do so in response to variation in the density of the fish. Question: Will the egret and the fish respond optimally to variation in prey density? Methods: We used two identical aviaries (7 m diameter), each with three separate pools of water (1.52 m diameter, 0.60 m deep, ∼1000 litres). In the centre of each pool was a single, solid disk (radius of 18.75, 22.75 or 36.75 cm) – the cover – which fish could hide under to protect themselves from egret predation. But fish could feed only in the risky habitat, i.e. the open water beyond the cover. In...
Evolutionary Ecology Research, 2018
Background: Predator and prey engage in a behavioural game in which the behavioural decision of o... more Background: Predator and prey engage in a behavioural game in which the behavioural decision of one affects that of the other. Behavioural games can be influenced by differential predation risk caused by habitat patchiness in the environment. Patches may provide prey with a differential risk of predation due to the size of area that provides refuge. The predator has to respond to the existence of patches with varying degrees of predation risk because this variable affects the time they spend foraging in each patch. Question: Will the predator and the prey respond optimally to each other in a behavioural game? Methods: We conducted behavioural experiments in two identical aviaries (7 m diameter), each with three separate pools (1.52 m diameter, 0.60 m deep, ∼1000 litres capacity). Each pool had two habitats, one a horizontal cover in the centre of the pool (the refuge), the other open water (the risky patch). We used little egrets (one per experiment) and goldfish (15 fish per pool) ...
Evolutionary Ecology Research, 2018
Background: A predator–prey relationship abounds with variables that might affect the behaviour o... more Background: A predator–prey relationship abounds with variables that might affect the behaviour of either species as it responds to the challenges of the predation game. In a series of experiments, we have studied the behavioural responses of goldfish (prey) and little egrets (predator) when brought together in a large laboratory apparatus – an aviary with three pools of water. To obtain a baseline, we measured their behaviour in an aviary without manipulating any variable (Katz et al., 2010). Because the results of that study suggested that both fish and egrets follow the rules of optimal foraging, we undertook a series of experiments in which we manipulated the number of food patches (Katz et al., 2014a), the number of fish per pool (Katz et al., 2014b; Vijayan et al., 2018a), and the size of goldfish refuges (Vijayan et al., 2018b). In each case, the results supported the hypothesis of optimal behaviour. Mitchell (2018, this issue) makes four predictions about the behaviours of b...
Canadian Journal of Zoology, 2018
To study how wildlife perceive recreating humans, we studied the habitat selection of a human com... more To study how wildlife perceive recreating humans, we studied the habitat selection of a human commensalist, the collared peccary (Pecari tajacu (Linnaeus, 1758)). We measured peccary activity patterns in an area of high human activity (Tumamoc Hill Desert Laboratory in Tucson, Arizona, USA) using a landscape-of-fear analysis. We examined whether the perception of risk from human activity interacted with the chemical (tannin) and mechanical (thorns) antipredator mechanisms of local plant species. The peccaries avoided food stations near a hiking trail. The population foraged less near houses, i.e., moderate human activity, than in the perceived safety of a small wadi. Plant defence treatments impacted the harvesting of food only in the safe zone, suggesting that risk trumps food selectivity. The strong effect of the hiking trail on habitat selection in this disturbance-loving species is an indicator of a much larger impact on sensitive species in conservation areas.
Proceedings of the Royal Society B: Biological Sciences, 2019
Refuges offer prey animals protection from predation, but increased time spent hiding can reduce ... more Refuges offer prey animals protection from predation, but increased time spent hiding can reduce foraging opportunities. Within social groups, individuals vary in their refuge use and willingness to forage in the presence of a predator. Here, we examine the relative foraging benefits and mortality costs associated with individual refuge use and foraging behaviour within groups of goldfish ( Carassius auratus ) under predation risk from an avian predator (little egret— Egretta garzetta ). We assessed individual order of emergence from the refuge and participation over 15 group foraging outings, and assigned each fish a daily outing index score. The individual fish that emerged from the refuge earlier than the other group members and that participated in more outings received high outing index scores and consumed more food compared with fish that tended to emerge in posterior positions and participate in fewer outings. However, individual fish that attained high outing index scores su...
Background: When exposed in previous experiments to a behavioural game in a three-pool laboratory... more Background: When exposed in previous experiments to a behavioural game in a three-pool laboratory theatre, common goldfish, Carassius auratus (the prey), and little egrets, Egretta garzetta (the predator), demonstrated optimal adjustments in their foraging and anti-foraging behaviours when confronted with different numbers of fish. Question: In a similar theatre with one, two or three pools and a fixed number of fish per pool, will predator and prey again solve the game and optimally adjust their foraging and anti-foraging behaviours? Methods: Experiments were conducted in two identical, circular aviaries (diameter 7 m) consisting of three circular pools (diameter 1.52 m), each of which could be covered so as to remove it from an experiment. We conducted experiments with one, two or three uncovered pools. Each pool had two available fish habitats: protected from predation but without food for fish, and exposed but with food. There were 15 goldfish in each experimental pool. One egret foraged in each aviary (none in controls). The egret moved at will among the pools. During six-hour observation periods, we observed, minute-by-minute, the distribution of fish among their habitats and the movement of the egret among the pools. In addition to compiling summary statistics of the behaviours, we counted the number of successful predation events and analysed the results to test their optimality. Results: As the number of pools changed, the egret changed its foraging behaviour, moving among the pools in a way that maximized its capture success. The time an egret spent hunting correlated with the number of pools available, thus it captured fish at a higher rate when more pools were available. Regardless of the number of pools, egrets captured the same number of goldfish per pool per day. The time that fish used the exposed habitat was negatively correlated with the time the egret foraged in a pool. However, even in one-pool trials, goldfish emerged from protected habitat occasionally, which sometimes led to their capture.
Journal of Animal Ecology, 2005
1. We tested the hypothesis that Gerbillus henleyi (de Winton 1903), the smallest species (10 g) ... more 1. We tested the hypothesis that Gerbillus henleyi (de Winton 1903), the smallest species (10 g) of a pssamophilic guild in Israel, is scarce on relatively productive dunes of the Israeli desert, due to negative interactions from the common G. allenby i (Thomas 1918) and G. pyramidum (Geoffroy 1825). 2. The alternative hypothesis was that scarcity on sand resulted from the size of its naked hind feet, that do not allow efficient locomotion on sand. 3. Despite their naked soles the weight-bearing surface of G. henleyi feet carry less mass/area than those of any other species. 4. We measured interaction coefficients with the two common species using fieldmanipulation experiments in two enclosures. 5. Habitat usage of G. henleyi changed from significantly preferring the stabilized sand, when alone, to significantly using the semistabilized dune, when G. allenbyi was also present. 6. We also estimated the interaction coefficients and calculated the G. henleyi 's isoclines competing with the two common gerbil species using a technique we developed elsewhere. 7. The stability analysis of the isoclines of G. henleyi competing with either G. allenbyi or with G. pyramidum suggests that stable coexistence occurs when G. henleyi is relatively scarce while the competitors are common. 8. Interspecific competition from either G. allenbyi or G. pyramidum accounts for 90•3% reduction in G. henleyi density, relative to when it is alone. 9. We concluded that the negative interactions from congeners was the major cause for the scarcity of G. henleyi on the relatively rich sand dunes of the Israeli desert.
Oikos, 1994
Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears... more Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit organization founded in 1995 to build trusted digital archives for scholarship. We work with the scholarly community to preserve their work and the materials they rely upon, and to build a common research platform that promotes the discovery and use of these resources. For more information about JSTOR, please contact [email protected].
Theoretical Population Biology, 1978
Oecologia, 1975
The populations of two coexisting species of Dipodomys (Heteromyidae, Rodentia) were manipulated ... more The populations of two coexisting species of Dipodomys (Heteromyidae, Rodentia) were manipulated on 10, large, unenclosed, trapping grids. These manipulations revealed that, although many kangaroo rats are established residents in an area, a large number are transient individuals who quickly occupy vacated habitats. On plots from which residents had been removed, transients settled at rates of up to 5% of carrying capacity per day. These immigrants were invariably of the same species that was removed, indicating a strong element of intraspecific competition with little or no evidence of competition between the species.Trapping records suggest that these species avoid competition through habitat selection. Dipodomys ordii prefer a grassier habitat, and D. merriami a habitat dominated by creosote bush. Apparent overlap in their utilization of habitats, based on sites of capture, predicts competition coefficients to be higher than those permitted by the theory of limiting similarity an...
Lecture Notes in Biomathematics
Oecologia
Behavioral games predators play among themselves may have profound effects on behavioral games pr... more Behavioral games predators play among themselves may have profound effects on behavioral games predators play with their prey. We studied the behavioral game between predators and prey within the framework of social foraging among predators. We tested how conspecific interactions among predators (little egret) change the predator-prey behavioral game and foraging success. To do so, we examined foraging behavior of egrets alone and in pairs (male and female) in a specially designed aviary consisting of three equally spaced pools with identical initial prey (comet goldfish) densities. Each pool was comprised of a risky microhabitat, rich with food, and a safe microhabitat with no food, forcing the fish to trade off food and safety. When faced with two versus one egret, we found that fish significantly reduced activity in the risky habitat. Egrets in pairs suffered reduced foraging success (negative intraspecific density dependence) and responded to fish behavior and to their conspecific by changing their visiting regime at the different pools-having shorter, more frequent visits. The time egret spent on each visit allowed them to match their long-term capture success rate across the environment to their capture success rate in the pool, which satisfies one aspect of optimality. Overall, egrets in pairs allocated more time for foraging and changed their foraging tactics to focus more on fish under cover and fish 'peeping' out from their shelter. These results suggest that both prey and predator show behavioral flexibility and can adjust to changing conditions as needed in this foraging game.
Species diversity in space and time, 2000
Species diversity in space and time, 2000
Paleobiology, 1991
Evolutionary progress is a trend that relaxes trade-off rules. It begins with the evolution of a ... more Evolutionary progress is a trend that relaxes trade-off rules. It begins with the evolution of a key adaptation. It continues with the spread of the key adaptation as the clade that contains it replaces some older clade that lacks it. Key adaptations are those that allow for improvement in at least one organismal function at a reduced fitness cost in other functions. Replacement almost certainly involves more than pure chance. It may not often involve competitive extinction. Instead, species from the new clade produce new species to replace already extinct species from the old clade. The key adaptation gives them a higher competitive speciation rate than old-clade sources of replacement. The process, termed incumbent replacement, proceeds at a rate limited by extinction rate. Thus, replacement often seems linked to mass extinction events. The incumbent-replacement hypothesis explains what we know about the replacement of straight-neck turtles (Amphichelydia) by those that can flex t...
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Papers by Michael Rosenzweig