Eviction Rates Research Articles

Cumulative or sequential assessment during hermit crab shell fights: effects of oxygen on decision rules.

Agonistic interactions between animals are often settled by the use of repeated signals which advertise the resource-holding potential of the sender. According to the sequential assessment game this repetition increases the accuracy with which receivers may assess the signal, but under the cumulative assessment model the repeated performances accumulate to give a signal of stamina. These models may be distinguished by the temporal pattern of signalling they predict and by the decision rules used by the contestants. Hermit crabs engage in shell fights over possession of the gastropod shells that they inhabit. During these interactions the two roles of signaller and receiver may be examined separately because they are fixed for the duration of the encounter. Attackers rap their shell against that of the defender in a series of bouts whereas defenders remain tightly withdrawn into their shells for the duration of the contest. At the end of a fight the attacker may evict the defender from its shell or decide to give up without first effecting an eviction; the decision for defenders is either to maintain a grip on its shell or to release the shell and allow itself to be evicted. We manipulated fatigue levels separately for attackers and defenders, by varying the oxygen concentration of the water that they are held in prior to fighting, and examined the effects that this has on the likelihood of each decision and on the temporal pattern of rapping. We show that the vigour of rapping and the likelihood of eviction are reduced when the attacker is subjected to low oxygen but that this treatment has no effect on rates of eviction when applied to defenders. We conclude that defenders compare the vigour of rapping with an absolute threshold rather than with a relative threshold when making their decision. The data are compatible with the cumulative assessment model and with the idea that shell rapping signals the stamina of attackers, but do not fit the predictions of the sequential assessment game.

Eviction rates

Eviction rates

The power of shell rapping influences rates of eviction in hermit crabs

Hermit crabs fight for ownership of shells, and shell exchange may occur after a period of shell rapping, involving the initiating or attacking crab bringing its shell rapidly and repeatedly into contact with the shell of the noninitiator or defender, in a series of bouts. The temporal pattern of rapping contains information about the motivation and/or relative resource holding potential (RHP) of the initiator and acts as a repeated signal of stamina. Here we investigated the role of the force with which the rapping is performed and how this is related to the temporal pattern of rapping by rubberizing the external surface of shells. Initiators that are prevented from rapping with their usual level of force persist with the activity for longer over the whole encounter but use fewer raps per bout and are less likely to effect an exchange than those supplied with control shells. The fact that the force of rapping affects the likelihood of a crab being victorious suggests that either the force of rapping contains information about motivation or RHP or that force directly affects noninitiators, reducing their ability to maintain an adequate grip on their shells. The data suggest that shell rapping is an agonistic signal rather than one that provides information useful to the noninitiator, as has been suggested by the negotiation model of shell exchange.

Evictions in the Welfare State - an Unintended Consequence of the Swedish Policy?

Despite a remarkable improvement in the general welfare of the Swedish population since the 1960s, the rate of housing evictions has rapidly increased in the same period This paper presents an analysis of factors associated with the growth in the eviction rate The main hypothesis models eviction rate growth as the unintended effect of Swedish housing policy, otherwise viewed as highly successful We also speculate about the relationship between homelessness and the evictions, suggesting that for Sweden the eviction rate and the prevalence of homelessness are negatively connected, i e. a high eviction rate is associated with a small number of homeless individuals. Data from two time periods, 1915-37 and 1950-81, are analyzed using ARIMA time series The period 1976-80 is, in addition, analyzed with pooled cross-section, time-series analysis.

An Empirical Analysis of Tenant Selection Under Federal Rent Supplement Programs: A First Step

The purpose of this study is to consider the question of whether characteristics of applicants for federally subsidized housing can be used in predicting whether one is accepted or rejected by management as a tenant. Using probit analysis, a statistical model was developed for use in assisting management in objectively screening applicants. Factors found significant in determining the probability of acceptance or rejection were credit ratings, character references, length of time employed, and student status. The percent of rent subsidized by government and sex of household head had little effect on applicant acceptance. Although a meaningful model for estimating the probability of eviction could not be developed, low eviction rates resulting from the tenant selection model suggest that it may serve as a reasonable proxy.