Who cares? Individual contributions to pup care by breeders vs non-breeders in the cooperatively breeding banded mongoose (<Emphasis Type="Italic">Mungos mungo</Emphasis>)

Knowledge of the investment rules adopted by breeders and non-breeders, and the factors that affect them, is essential to understanding cooperative breeding as part of a life-history tactic. Although the factors that affect relative contributions to care of young have been studied in some cooperative bird species, there is little data on mammals, making coherent generalisations within mammals and across taxa difficult. In this study, we investigate individual contributions to pup escorting, a strong predictor of offspring provisioning, in the banded mongoose (Mungos mungo), a cooperatively breeding mammal in which reproductive skew is low. Contributions by those under a year old (which virtually never breed) increased with age and body weight but were generally low. Among older age classes (yearlings and adults), individuals that had not bred in the current litter generally contributed less to escorting than those that had bred (with the exception of yearling males). In addition, females that did not breed reduced their investment if they were heavy presumably because such females are more likely to breed in the following event and benefit from saving resources for this. The generally greater contributions by breeders in banded mongooses contrast with the recent findings in meerkats (Suricata suricatta), another obligatorily cooperative mongoose with similar group size but wherein reproductive skew is high. Our results suggest that relative contributions by breeders vs non-breeders are not dependent on group size but on the ratio of breeders to carers and the probability that non-breeders will breed in the near future.     

Measuring biological diversity

The diversity of a set of species refers to the joint dissimilarity of the species in the set. This paper discusses the measurement of diversity from the set of pairwise distances between the species in the set. A measure called the effective number of species is developed from a non-parametric probability inequality and is shown to have a simple interpretation in terms of comparing linear experiments.     

Local likelihood disease clustering: development and evaluation

This paper illustrates a method based on local likelihood (LL) for detecting disease clusters. The approach is based on estimating a lasso distance for each region: within which regions are considered to be clustered. An important advantage in implementing this approach is that it does not require any special Monte Carlo Markov Chain (MCMC) algorithm, e.g., reversible jump MCMC, which is essential in hidden Markov model approach. Another advantage is that extending the model to incorporate covariates is straightforward. We illustrate three ways of doing this by using Eastern Germany lip cancer data. By using simulated data, we have made a comparison with the BYM model [Besag et al. (1991) Annals of the Institute of Statistical Mathematics, 43, 1–59] and the mixture model [Lawson and Clark (2002) Disease Mapping and Risk Assessment for Public Health, Chapman and Hall]. We also did a limited examination of the ability of the LL model to recover true relative risk under different priors for lasso parameter. In order to check the edge effects, which has been overlooked in many spatial clustering models for disease mapping but deserves special attention as it lacks observable neighbors, we have adapted here a simple approach to observe the changes in relative risks when the edge regions are omitted. An erratum to this article is available at .     

Temporal trends in the sources of PCDD/Fs to and around the Venice Lagoon

Two salt marsh cores were collected from the Venice Lagoon, Italy, and analysed for PCDD/Fs. The samples were undisturbed and had an approximately constant accumulation rate. Radiochemical chronologies were established for the different core sections. The PCDD/F pattern in the surficial layers was very similar to that of atmospheric deposition measured in the same area. However, the pattern changed with increasing depth and was very different in the deeper sections, where the highest PCDD/F concentrations were measured. This layer was dated around the 1950s. Deeper layers have a profile similar to the surficial one. Undisturbed salt marsh cores appear to be a reliable tool for the reconstruction of temporal trends in the atmospheric deposition of persistent organic pollutants. It is proposed that the trends in the core reflect atmospheric deposition that probably results from the sum of two different contributions: emissions of the industrial district of Porto Marghera on the edge of the lagoon and the regional background.     

Hydrocarbons in Sand Crabs (Emeritaanaloga) from Southern California (U.S.A.)

$\text{Emerita}$$\text{analoga}$ (Crustacea:Hippidae) from three southern California (U.S.A.) beaches contained 0.9 to 24.1 μg/g dry wt saturated hydrocarbons, and 3.6 to 21.4 μg/g dry wt unsaturated hydrocarbons. Major constituents were (in wt. % total): n-alkanes (13.1%), heneicosapentaene plus heneicosahexaene (1.0%), squalene (5.1%), and unidentified polyenes (7.8%). Crabs from beaches exposed to small boat traffic and natural oil seepage were slightly and severely tainted, respectively, with petroleum hydrocarbons. Animals from San Nicolas Island (85 km offshore) contained only biogenic compounds.     

Incubation feeding by helpers influences female nest attendance in the green woodhoopoe,<Emphasis Type="Italic"> Phoeniculus purpureus</Emphasis>

In many bird species, the female alone incubates the eggs, but the male provides her with some food during the incubation period. In cooperatively breeding species, helpers might be expected to assist the breeding male in provisioning the female, but their contribution has been generally ignored. Here, I show that in the green woodhoopoe, Phoeniculus purpureus, the breeding male and helpers of both sexes bring food to the incubating female. The helpers did not increase the overall amount of provisioning the female received: groups of all sizes delivered a similar amount of food per hour. Helpers did, however, reduce the workload of the breeding male. Male and female helpers provisioned incubating females equally, as expected in a species where both sexes are likely to derive equal benefits from their helping behaviours. Female nest attendance was positively related to the level of group provisioning, but only in the short term. Thus, the female-nutrition hypothesis, which suggests that incubation feeding can provide an important source of energy to the breeding female, is supported in the green woodhoopoe.Communicated by I. Hartley