Beginning with Emlen (1966) and MacArthur and Pianka (1966) and extending through the last ten years, several authors have sought to predict the foraging behavior of animals by means of mathematical models. These models are very similar,in that they all assume that the fitness of a foraging animal is a function of the efficiency of foraging measured in terms of some "currency" (Schoener, 1971) -usually energy- and that natural selection has resulted in animals that forage so as to maximize this fitness. As a result of these similarities, the models have become known as "optimal foraging models"; and the theory that embodies them, "optimal foraging theory." The situations to which optimal foraging theory has been applied, with the exception of a few recent studies, can be divided into the following four categories: (1) choice by an animal of which food types to eat (i.e., optimal diet); (2) choice of which patch type to feed in (i.e., optimal patch choice); (3) optimal allocation of time to different patches; and (4) optimal patterns and speed of movements. In this review we discuss each of these categories separately, dealing with both the theoretical developments and the data that permit tests of the predictions. The review is selective in the sense that we emphasize studies that either develop testable predictions or that attempt to test predictions in a precise quantitative manner. We also discuss what we see to be some of the future developments in the area of optimal foraging theory and how this theory can be related to other areas of biology. Our general conclusion is that the simple models so far formulated are supported are supported reasonably well by available data and that we are optimistic about the value both now and in the future of optimal foraging theory. We argue, however, that these simple models will requre much modification, espicially to deal with situations that either cannot easily be put into one or another of the above four categories or entail currencies more complicated that just energy.

Citation classic - optimal foraging - a selective review of theory and tests

Traditionally, measurement of the acute toxicity of pesticides to beneficial arthropods has relied largely on the determination of an acute median lethal dose or concentration. However, the estimated lethal dose during acute toxicity tests may only be a partial measure of the deleterious effects. In addition to direct mortality induced by pesticides, their sublethal effects on arthropod physiology and behavior must be considered for a complete analysis of their impact. An increasing number of studies and methods related to the identification and characterization of these effects have been published in the past 15 years. Review of sublethal effects reported in published literature, taking into account recent data, has revealed new insights into the sublethal effects of pesticides including effects on learning performance, behavior, and neurophysiology. We characterize the different types of sublethal effects on beneficial arthropods, focusing mainly on honey bees and natural enemies, and we describe the methods used in these studies. Finally, we discuss the potential for developing experimental approaches that take into account these sublethal effects in integrated pest management and the possibility of integrating their evaluation in pesticide registration procedures.

The Sublethal Effects of Pesticides on Beneficial Arthropods

What determines the timing of human actions? A big question, but the science of human dynamics is here to tackle it. And its predictions are of practical value: for example, when ISPs decide what bandwidth an institution needs, they use a model of the likely timing and activity level of the individuals. Current models assume that an individual has a well defined probability of engaging in a specific action at a given moment, but evidence that the timing of human actions does not follow this pattern (of Poisson statistics) is emerging. Instead the delay between two consecutive events is best described by a heavy-tailed (power law) distribution. Albert-Laszlo Barabasi proposes an explanation for the prevalence of this behaviour. The ‘bursty’ nature of human dynamics, he finds, is a fundamental consequence of decision making. The dynamics of many social, technological and economic phenomena are driven by individual human actions, turning the quantitative understanding of human behaviour into a central question of modern science. Current models of human dynamics, used from risk assessment to communications, assume that human actions are randomly distributed in time and thus well approximated by Poisson processes1,2,3. In contrast, there is increasing evidence that the timing of many human activities, ranging from communication to entertainment and work patterns, follow non-Poisson statistics, characterized by bursts of rapidly occurring events separated by long periods of inactivity4,5,6,7,8. Here I show that the bursty nature of human behaviour is a consequence of a decision-based queuing process9,10: when individuals execute tasks based on some perceived priority, the timing of the tasks will be heavy tailed, with most tasks being rapidly executed, whereas a few experience very long waiting times. In contrast, random or priority blind execution is well approximated by uniform inter-event statistics. These finding have important implications, ranging from resource management to service allocation, in both communications and retail.

The origin of bursts and heavy tails in human dynamics

Worldwide decline of the entomofauna: A review of its drivers

http://romisatriawahono.net/lecture/rm/survey/softcomputing/Boussaid%20-%20Optimization%20Metaheuristics%20-%202013.pdf

A survey on optimization metaheuristics

In the 'dance language' of honeybees, the dancer generates a specific, coded message that describes the direction and distance from the hive of a new food source, and this message is displaced in both space and time from the dancer's discovery of that source. Karl von Frisch concluded that bees 'recruited' by this dance used the information encoded in it to guide them directly to the remote food source, and this Nobel Prize-winning discovery revealed the most sophisticated example of non-primate communication that we know of. In spite of some initial scepticism, almost all biologists are now convinced that von Frisch was correct, but what has hitherto been lacking is a quantitative description of how effectively recruits translate the code in the dance into flight to their destinations. Using harmonic radar to record the actual flight paths of recruited bees, we now provide that description.

/pdf/the-flight-paths-of-honeybees-recruited-by-the-waggle-dance-1z3wwfz03g.pdf

The flight paths of honeybees recruited by the waggle dance

By using harmonic radar, we report the complete flight paths of displaced bees. Test bees forage at a feeder or are recruited by a waggle dance indicating the feeder. The flights are recorded after the bees are captured when leaving the hive or the feeder and are released at an unexpected release site. A sequence of behavioral routines become apparent: (i) initial straight flights in which they fly the course that they were on when captured (foraging bees) or that they learned during dance communication (recruited bees); (ii) slow search flights with frequent changes of direction in which they attempt to “get their bearings”; and (iii) straight and rapid flights directed either to the hive or first to the feeding station and then to the hive. These straight homing flights start at locations all around the hive and at distances far out of the visual catchment area around the hive or the feeding station. Two essential criteria of a map-like spatial memory are met by these results: bees can set course at any arbitrary location in their familiar area, and they can choose between at least two goals. This finding suggests a rich, map-like organization of spatial memory in navigating honey bees.

https://www.pnas.org/content/pnas/102/8/3040.full.pdf

Honey bees navigate according to a map-like spatial memory

Three neonicotinoids, imidacloprid, clothianidin and thiacloprid, agonists of the nicotinic acetylcholine receptor in the central brain of insects, were applied at non-lethal doses in order to test their effects on honeybee navigation. A catch-and-release experimental design was applied in which feeder trained bees were caught when arriving at the feeder, treated with one of the neonicotinoids, and released 1.5 hours later at a remote site. The flight paths of individual bees were tracked with harmonic radar. The initial flight phase controlled by the recently acquired navigation memory (vector memory) was less compromised than the second phase that leads the animal back to the hive (homing flight). The rate of successful return was significantly lower in treated bees, the probability of a correct turn at a salient landscape structure was reduced, and less directed flights during homing flights were performed. Since the homing phase in catch-and-release experiments documents the ability of a foraging honeybee to activate a remote memory acquired during its exploratory orientation flights, we conclude that non-lethal doses of the three neonicotinoids tested either block the retrieval of exploratory navigation memory or alter this form of navigation memory. These findings are discussed in the context of the application of neonicotinoids in plant protection.

/pdf/neonicotinoids-interfere-with-specific-components-of-20pjkvcft5.pdf

Neonicotinoids interfere with specific components of navigation in honeybees.

Honey bees (Apis mellifera) are regularly faced with the task of navigating back to their hives from remote food sources. They have evolved several methods to do this, including compass-directed "vector" flights and the use of landmarks. If these hive-centered mechanisms are disrupted, bees revert to searching for the hive, but the nature -and efficiency of their searching strategy have hitherto been unknown. We used harmonic radar to record the flight paths of honey bees that were searching for their hives. Our subsequent analysis of these paths revealed that they can be represented by a series of straight line segments that have a scale-free, Levy distribution with an inverse-square-law tail. We show that these results, combined with the "no preferred direction" characteristic of the segments, demonstrate that the bees were flying an optimal search pattern. Levy movements have already been identified in a number of other animals. Our results are the best reported example where the movements are mostly attributable to the adoption of an optimal, scale-free searching strategy.

Displaced honey bees perform optimal scale-free search flights

Learning trials distributed over time lead to better memory than learning trials squeezed into short periods of time. Jost (1897), who elaborated on the original findings by Ebbinghaus (1885), was the first to formulate a theory supposing a contraintuitive, even perplexing interrelation between short-term forgetting and long-term strengthening of memory. In his words, “Given equal associative strength, the older the memory trace at the time of learning repetition, the less forgetting over the long term.” The “paradox of spaced practice” (Bjork and Allen 1970) was assumed to lie in the fact that longer intervals between learning trials should lead to less memory on a trial-to-trial basis, but multiple units of less memory should finally lead to stronger long-term memory.

The conceptual basis for interpreting the spacing effect is the notion of memory dynamics (James 1890; Muller and Pilzecker 1900; Squire 1987). Each learning trial is thought to initiate an intrinsic process of memory formation that leads to final memory by constructive (memory consolidation) and destructive (forgetting) processes. Studies of many species have shown that when training involves multiple trials, the time interval between trials is an important variable in the efficacy of accumulating training effects and the strength of retention (Carew et al. 1972; Fanselow and Tighe 1988; Tully et al. 1994; Spieler and Balota 1996; Kogan et al. 1997; Hermitte et al. 1999; Muzzio et al. 1999; Beck et al. 2000; Wu et al. 2001). The paradigms tested were taste aversion conditioning, fear conditioning, blink conditioning, olfactory aversion training, episodic priming, and learning nonsense syllables. In addition to humans, a wide range of animals was studied (Drosophila, the marine mollusks Aplysia and Hermissenda, the crab Chasmagnathus, rats, and rabbits). The dynamics and interdependence of the constructive and destructive (forgetting) memory processes, and, particularly, their reliance on external and internal parameters are, however, mostly unknown. Because the spacing effect is a robust behavioral phenomenon and calls for a mechanistic explanation, it would be desirable to parameterize conditions controlling the effect. In particular, the relationship between parameters controlling the acquisition process and retention over longer test intervals has not yet been systematically studied. Manipulations of the learned stimuli, the strength of reinforcement, and training schedules lead to different levels of initial learning and need to be examined with respect to their effect on the spacing phenomenon.

In the past honeybees (Apis mellifera) have been used successfully to describe memory dynamics after single- or multiple-trial appetitive learning both in color learning by free-flying bees and in olfactory proboscis conditioning (for review, see Menzel 1999; Menzel and Muller 1996). For free-flying honeybees it was discovered that a single conditioning trial leads to a dual-phase retention function with high retention at very short ( 5 min) intervals, and with a dip around 3 min, indicating a consolidation process in the time range of several minutes after learning. Multiple learning trials facilitate consolidation into long-lasting memory (more than several days). Consolidation is accompanied by increasing resistance to extinction (Menzel 1990) and reduced preparedness for reversal learning (Menzel 1979). Furthermore, the time course of consolidation was found to depend on the strength of reward (Menzel 1968). Using the olfactory conditioning paradigm, one can demonstrate the same dual-phase time course of retention as in free-flying bees, and the effects on resistance to extinction and reversal learning (Menzel 1990). In addition, Smith (1991) found that generalization between odors after a single odor conditioning trial is different in the short (30 sec) and longer term (15–30 min) ranges, indicating a change in memory content during consolidation (see also Menzel 1990). In earlier studies (Bitterman et al. 1983; Sandoz et al. 1995) multiple learning trials with either very long or very short intertrial intervals (ITIs) between 1 and 20 min did not lead to different acquisition and retention. However, an analysis that also tested intermediate ITIs found a nonmonotonous dependence of long-term memory (LTM) on ITI (Gerber et al. 1998). LTM after 4 d is high for short (1 min) and long (20 min) ITIs, but low for an intermediate (3 min) ITI. Interestingly, retention after 1 d was not affected by the ITI, leading to the working hypothesis that 1-d and 4-d retention might have different mechanistic bases. Concerning the relation of retention and acquisition, the authors (Gerber et al. 1998) argued that in their data set, differences in the levels of acquisition and retention are doubly dissociated, and that acquisition performance therefore does not translate one-to-one into retention test performance. The nonmonotonous trial spacing effect is therefore independent of the process of acquisition, and does not depend on differences in short-term retention, but may depend on a process of consolidation between trials that is specifically obstructed for ITIs of 3 min. Such a consolidation process affects only late LTM, a long-term memory phase that develops after 1 d, and requires protein synthesis (Grunbaum and Muller 1998; Wustenberg et al. 1998; Menzel 1999).

These results support the conclusion that the time-dependence of retention is strongly related to the spacing effect. Because the level of retention also depends on parameters influencing acquisition (e.g., the salience of the conditioned stimulus, CS; the strength of the unconditional stimulus, US; the number of CS/US pairings), one may ask whether the level of acquisition (instead of or in addition to the timing of repeated trials) may control consolidation. We accordingly manipulated acquisition over a wide range by varying the CS and US strengths and the number of acquisition trials. We find that the spacing of learning trials is the dominant factor both for acquisition and retention. In addition, we find a prominent difference in retention at the late long-term memory phase (>2 d after conditioning). Spaced conditioning trials induce a consolidation process that can be selectively inhibited by blocking protein synthesis during acquisition.

/pdf/massed-and-spaced-learning-in-honeybees-the-role-of-cs-us-5brgfkbvmy.pdf

Uwe Greggers

Papers

The flight paths of honeybees recruited by the waggle dance

Honey bees navigate according to a map-like spatial memory

Neonicotinoids interfere with specific components of navigation in honeybees.

Displaced honey bees perform optimal scale-free search flights

Massed and spaced learning in honeybees: the role of CS, US, the intertrial interval, and the test interval.