捕食者——猎物功能反应模型初探

本文通过分析在捕食的情况下猎物种群的平均绝对增长速率与捕食效应的关系以及捕食者的捕食平均绝对速率与猎物密度的关系,建立了捕食者——猎物功能反应的一般模型:dHa/dHt=A(Ha/Ht)f(Ht) 其中,A为捕食者与猎物行为常数,f(Ht)为待定函数。 (1)在捕食速率与猎物密度无关时,这时f(Ht)=常数。其功能反应模型为: 其中,a为攻击速率,b^(-1)为猎物群体防御系数,H_k为捕食量阈值。当b=1时,即表示猎物无群体防御效应,这时模型即成为HollingI型反应模型。 (2)在捕食速率与猎物密度有关的情况下,通过对最大捕食率限制因素的分析,结果认为捕食平均绝对速率随着猎物密度的增加而下降。因而对f(Ht)进行了如下假设: (a)设f(Ht)=1/Ht,代入一般方程式后得Ha=ae^(b/Dt) 其中,a为最大捕食量,b为最佳寻找猎物密度。此模型是描述Ⅲ型曲线。但当b=1时,模型实际上是描述Ⅱ型反应。 (b)设f(Ht)=1/(1+bHt)时,得功能反应模型为:Ha=a(bHt/1+bHt)~e 其中,a为最大捕食量,(c—1)/b为最佳寻找猎物密度。当c>1时,模型描述Ⅲ型曲线。当c=1时模型即为圆盘方程。如果进一步对f(Ht)进行假设可以得到一系列的新的功能反应模型。通过对上面模型的分析,笔者认为功能反应模型按Holling的Ⅰ、Ⅱ、Ⅲ型反应相应划分是不方便的。建议按“捕食速率与猎物密度无关或有关”两个类型划分。并认为Ⅲ型模型在昆虫中也能得到较广泛的应用。

Owls and Mobbing Behavior： Anecdotal Observations

Mobbing behavior is an important and widespread antipredatory behavior. This is a well-known behavior especially in birds. There are many studies about mobbing in birds, and most of them use owls as a model of predator. However it is not clear how mobbing works when a predator assume a role of a prey. In this paper we organize field observations, which were taken on records of mobbing behaviors performed by owls or by other animals against them. These observations were collected nearby four Brazilian cities in South-Eastern and Central Brazil： Joao Monlevade / MG, Sacramento / MG Baguari / MG and Cacu / GO. Events of mobbing behavior have always involved prey（s） and predator（s） thus, in this study we presents mobbing events which species of owl always were involved, and beside the owls, other animals like mammals or raptors. These records are important due to their infrequency and problems to be detected in natural field conditions. It is rare mobbing events when an owl assumes a role of a prey, and there are few studies that show the mobbing by the predator optics. The present data may contribute for elucidation of mobbing behavior intrinsic aspects.

ANALYSIS OF A PREDATOR-PREY MODEL WITH DISEASE IN THE PREY

In this paper, we discuss the behavior of a predator-prey model with disease in the prey with and without stochastic perturbation, respectively. First, we briefly give the dynamic of the deterministic system, by analyzing stabilities of its four equilibria. Then, we consider the asymptotic behavior of the stochastic system. By Lyapunov analysis methods, we show the stochastic stability and its long time behavior around the equi- librium of the deterministic system. We obtain there are similar properties between the stochastic system and its corresponding deterministic system, when white noise is small. But large white noise can make a unstable deterministic system to be stable.

Permanence of a diffusive Leslie-Gower predator-prey model incorporating a prey refuge

The diffusive Leslie-Clower predator-prey model incorporating a prey refuge is recon- sidered here. Sufficient and necessary conditions which guarantee the predator and the prey species to be permanent are obtained, and our results supplement earlier ones.

Predator-prey distance and latency to flee from an immobile predator： functional relationship and importance

When an immobile prey has detected an immobile predator nearby, predation risk is greater when the predator is closer. Consequently, prey flee with shorter latency as standing distance （predator-prey distance when both are still） decreases. Since it was first reported in 2009, this relationship has been confirmed in the few species studied. However, little is known about the functional relationship between standing distance and latency to flee （LF）. We hypothesized that LF increases as standing distance increases at short distances, but reaches a plateau at longer distances where prey can escape reliably if attacked. We simulated immobile predators by moving slowly into positions near striped plateau lizards Sceloporus virgatus, stopping and then remaining immobile, and recording LF from the stopping time. LF increased from shorter to longer standing distances in a decelerating manner. The relationship was concave downward, and LF was indistinguishable among the longer standing distance groups. Latency to flee appears to reach a plateau or approach an asymptotic value as stand- ing distance increases. The effect size of standing distance was large, indicating that S. virgatus sensi- tively adjusts LF to the level of risk associated with standing distance. Relationships between risk assessment and theoretical zones associated with risk, its assessment by prey, and escape decisions are discussed. Effect sizes of standing distance were substantial to large in all studies to date, indicating that standing distance is an important predation risk factor when both predator and prey are immobile.

Effects of historically familiar and novel predator odors on the physiology of an introduced prey

Predator odors can elicit fear responses in prey and predator odor recognition is generally associated with physiological responses. Prey species are often more likely to respond to the odor of familiar ra- ther than alien predators. However, predator na＇ivety in an introduced prey species has rarely been investigated. We examined the physiological response, as shown by changes in ventilatory vari- ables, of an introduced terrestrial herbivore, the European rabbit Oryctolagus cuniculus, in Australia, to the odor of potential predators and to control odors （distilled water and horse）, to explore if res- ponses were limited to historical （cat and fox） predators, or extended to historically novel predators （snake and quoll）. All odors except distilled water elicited a response, with rabbits showing long- term higher respiratory frequencies and lower tidal volumes after introduction of the odors, indi- cating an increase in alertness. However, the intensity of the rabbits＇ reaction could not be directly linked to any pattern of response with respect to the history of predator-prey relationships. Rabbits exhibited significantly stronger reactions in response to both cat and quoll odors than they did to dis- tilled water, but responses to horse, fox, and snake odor were similar to that of water. Our results show that the introduced rabbit can respond to both historical and novel predators in Australia, and suggest that shared evolutionary history is not necessarily a prerequisite to predator odor recognition.

Almost periodic solution of a modified Leslie-Gower predator-prey model with Holling-type II schemes and mutual interference

In this paper, we consider a modified Leslie-Clower predator prey model with Holling- type II schemes and mutual interference. By applying the comparison theorem of the differential equation and constructing a suitable Lyapunov function, sufficient conditions which guarantee the permanence and existence of a unique globally attractive positive almost periodic solution of the system are obtained. Our results not only supplement but also improve some existing ones.

Do predator energy demands or previous exposure influence protection by aposematic coloration of prey？

Growing evidence exists that aposematic and toxic prey may be included in a predator＇s diet when the predator experiences physiological stress. The tree sparrow Passer montanus is known to have a significant portion of aposematic and toxic ladybirds in its natural diet. Here, we present experi- ments testing the attack and eating rate of the tree sparrow toward the invasive aposematic harle- quin ladybird Harmonia axyridis. We wondered whether the sparrow＇s ability to prey on native ladybirds predisposes them to also prey on harlequin ladybirds. We compared the attack and eat- ing rates of tree sparrows of particular age and/or experience classes to test for any changes during ontogeny （hand-reared x young wild-caught xadult wild-caught） and with differing perceived lev- els of physiological stress （summer adult ~ winter adult）. Winter adult tree sparrows commonly at- tacked and ate the offered ladybirds with no evidence of disgust or metabolic difficulties after in- gestion. Naive and wild immature tree sparrows attacked the ladybirds but hesitated to eat them. Adult tree sparrows caught in the summer avoided attacking the ladybirds. These results suggest that tree sparrows are able to cope with chemicals ingested along with the ladybirds. This pre- adaptation enables them to include ladybirds in their diet; though they commonly do this only in times of shortage in insect availability （winter）. Young sparrows showed avoidance toward the chemical protection of the ladybirds.