Predicting animal home-range structure and transitions using a multistate Ornstein-Uhlenbeck biased random walk
Article in Press, The home-range concept is central in animal ecology and behavior, and numerous mechanistic models have been developed to understand home range formation and maintenance. These mechanistic models usually assume a single, contiguous home range. Here we describe and implement a simple home-range model that can accommodate multiple home-range centers, form complex shapes, allow discontinuities in use patterns, and infer how external and internal variables affect movement and use patterns. The model assumes individuals associate with two or more home-range centers and move among them with some estimable probability. Movement in and around home-range centers is governed by a two-dimensional Ornstein-Uhlenbeck process, while transitions between centers are modeled as a stochastic state-switching process. We augmented this base model by introducing environmental and demographic covariates that modify transition probabilities between home-range centers and can be estimated to provide insight into the movement process. We demonstrate the model using telemetry data from sea otters (Enhydra lutris) in California. The model was fit using a Bayesian Markov Chain Monte Carlo method, which estimated transition probabilities, as well as unique Ornstein-Uhlenbeck diffusion and centralizing tendency parameters. Estimated parameters could then be used to simulate movement and space use that was virtually indistinguishable from real data. We used Deviance Information Criterion (DIC) scores to assess model fit and determined that both wind and reproductive status were predictive of transitions between home-range centers. Females were less likely to move between home-range centers on windy days, less likely to move between centers when tending pups, and much more likely to move between centers just after weaning a pup. These tendencies are predicted by theoretical movement rules but were not previously known and show that our model can extract meaningful behavioral insight from complex movement data.
Material picked from large collection of coralline algae
Trawl F-1; sample 14/28; Periphyla jellies
Variability of upper ocean thermohaline structure during a MJO event from DYNAMO aircraft observations
This paper reports upper ocean thermohaline structure and variability observed during the life cycle of an intense Madden Julian Oscillation (MJO) event occurred in the southern tropical Indian Ocean (14°S-Eq, 70°E-81°E). Water column measurements for this study were collected using airborne expendable probes deployed from NOAA's WP-3D Orion aircraft operated as a part of Dynamics of MJO field experiment conducted during November-December, 2011. Purpose of the study is twofold; (1) to provide a statistical analysis of the upper ocean properties observed during different phases of MJO and, (2) to investigate how the upper ocean thermohaline structure evolved in the study region in response to the MJO induced perturbation. During the active phase of MJO, mixed layer depth (MLD) had a characteristic bimodal distribution. Primary and secondary modes were at ∼ 34 m and ∼ 65 m respectively. Spatial heterogeneity of the upper ocean response to the MJO forcing was the plausible reason for bimodal distribution. Thermocline and isothermal layer depth deepened respectively by 13 m and 19 m from the suppressed through the restoring phase of MJO. Thicker (> 30 m) barrier layers were found to occur more frequently in the active phase of MJO, associated with convective rainfalls. Additionally, the water mass analysis indicated that, in the active phase of this MJO event the sub-surface was dominated by Indonesian throughflow, nonetheless intrusion of Arabian Sea high saline water was also noted near the equator.
Trade-offs between reproduction and health in free-ranging African striped mice
Energy is limited and must be allocated among competing life-history traits. Reproduction is considered one of the most energetically demanding life-history stages. Therefore, the amount of energy an individual invests in reproduction might carry fitness costs through reduced energy allocation to other activities such as health maintenance. We investigated whether reproduction impacts health in the seasonally breeding African striped mouse (Rhabdomys pumilio). We measured health in individuals that reproduced (breeders) and individuals that did not reproduce (their adult offspring) and tested whether: (1) breeders’ health before reproduction was similar to that of their offspring (representing a baseline); (2) breeders’ health deteriorated after reproduction; (3) breeders’ health after reproduction was worse than that of their offspring. We collected blood samples from 12 breeding females and 11 breeding males both at the onset and at the end of the breeding season and from 12 adult daughters and 11 adult sons that did not reproduce at the end of the breeding season. Health was assessed using serum biochemistry analysis with VetScan Abaxis. Breeders differed considerably in their health before and after reproduction, particularly in parameters associated with digestion (lower amylase in males), metabolism (lower albumin, alkaline phosphatase, creatinine and glucose), osmoregulation (lower potassium and phosphorous in females) and immunity (higher globulin and altered alanine aminotransferase). Our results suggest that with the onset of breeding striped mice shifted their energy allocation from maintaining health to reproduction, indicating that investment into reproduction carries significant health costs.