Social structure and habitat design affect the impact of a novel feeding enrichment for alligators.

Providing enrichment that expands the range of behavioral opportunities associated with food acquisition and environmental exploration is an important contributing factor to the well-being of zoo animals. These behaviors can be difficult to promote in carnivores, given their foraging strategies and the logistical, ethical, and financial challenges of providing live prey. In this study, we introduced a novel feeding enrichment to Jacksonville Zoo and Gardens' five adult American alligators (Alligator mississippiensis) in an attempt to simulate a live prey organism within the exhibit and promote natural hunting behaviors like chasing and lunging, as well as increase daily activity levels. The enrichment promoted some behavioral goals for two of the alligators, but it did not promote behavioral goals for the other three alligators. This could have been due to a variety of factors including an existing dominance hierarchy amongst the group's females and the resulting spatial distribution of individuals across a habitat with only one water feature. Our results suggest that female alligators may carve out territories and avoid overlapping space usage with other females during the warmest months of the year. Given the outcomes and limitations of this enrichment strategy, we provide recommendations for this group specifically as well as future enrichment efforts in the general captive crocodilian population.

American alligator (Alligator mississippiensis) weight gain in captivity and implications for captive reptile body condition.

The body condition of an animal is an indicator of health status and is dependent upon many factors, some of which can vary between wild and captive settings. Despite this, there have not been many studies on how captivity affects body condition relative to wild animal populations. This study explores the body condition of captive and wild American alligators (Alligator mississippiensis) because reptiles are frequently overlooked in studies of captive animal health and because alligators are well-represented in captivity. We collected body condition data from 209 captive alligators and 935 wild alligators throughout Florida and southeastern Georgia and compared the relationships between body condition and body length for each group. We found that captive alligators exhibited significantly higher body condition values as they aged, and that this result was driven by the difference between captive and wild males. Body condition values for captive juveniles did not differ from wild juveniles, but they differed when comparing adults. Our results suggest that factors such as diet and movement rates play major roles in determining alligator body condition and that body condition may be an important metric for monitoring captive alligator health, especially for older adult males.

The application of Bayesian hierarchical models to quantify individual diet specialization.

Intraspecific variation in ecologically relevant traits is widespread. In generalist predators in particular, individual diet specialization is likely to have important consequences for food webs. Understanding individual diet specialization empirically requires the ability to quantify individual diet preferences accurately. Here we compare the currently used frequentist maximum likelihood approach, which infers individual preferences using the observed prey proportions to Bayesian hierarchical models that instead estimate these proportions. Using simulated and empirical data, we find that the approach of using observed prey proportions consistently overestimates diet specialization relative to the Bayesian hierarchical approach when the number of prey observations per individual is low or the number of prey observations vary among individuals, two common features of empirical data. Furthermore, the Bayesian hierarchical approach permits the estimation of point estimates for both prey proportions and their variability within and among levels of organization (i.e., individuals, experimental treatments, populations), while also characterizing the uncertainty of these estimates in ways inaccessible to frequentist methods. The Bayesian hierarchical approach provides a useful framework for improving the quantification and understanding of intraspecific variation in diet specialization studies.

Predator community composition is linked to soil carbon retention across a human land use gradient.

Soil carbon (C) storage is a major component of the carbon cycle. Consensus holds that soil C uptake and storage is regulated by plant-microbe-soil interactions. However, the contribution of animals in aboveground food webs to this process has been overlooked. Using insights from prior long-term experimentation in an old-field ecosystem and mathematical modeling, we predicted that the amount of soil C retention within a field should increase with the proportion of active hunting predators comprising the aboveground community of active hunting and sit-and-wait predators. This comes about because predators with different hunting modes have different cascading effects on plants. Our test of the prediction revealed that the composition of the arthropod predator community and associated cascading effects on the plant community explained 41% of variation in soil C retention among 15 old fields across a human land use gradient. We also evaluated the potential for several other candidate factors to explain variation in soil C retention among fields, independent of among-field variation in the predator community. These included live plant biomass, insect herbivore community composition, soil arthropod decomposer community composition, degree of land use development around the fields, field age, and soil texture. None of these candidate variables significantly explained soil C retention among the fields. The study offers a generalizable understanding of the pathways through which arthropod predator community composition can contribute to old-field ecosystem carbon storage. This insight helps support ongoing efforts to understand and manage the effects of anthropogenic land use change on soil C storage.

Temperature dependence of predation stress and the nutritional ecology of a generalist herbivore.

Prey at risk of predation may experience stress and respond physiologically by altering their metabolic rates. Theory predicts that such physiological changes should alter prey nutrient demands from N-rich to C-rich macronutrients and shift the balance between maintenance and growth/reproduction. Theory further suggests that for ectotherms, temperature stands to exacerbate this stress. Yet, the interactive effects of predation stress and temperature stress on diet, metabolism, and survival of ectotherms are not well known. This knowledge gap was addressed with a laboratory study in which wild juvenile grasshoppers were collected, assigned to one of three groups, and raised at three different temperatures. All grasshoppers had access to equal quantities of two diets composed of opposite carbohydrate : protein ratios. Half of the individuals in each temperature group were exposed to predation risk cues from spider predators, while the other half were kept in risk free conditions. Grasshoppers consumed more carbohydrates when exposed to predation risk, but consumption favored greater protein intake as temperature increased. Moreover, the difference in carbohydrate intake between risk cue and risk free treatments diminished as temperature increased. Furthermore, variability between individual consumption patterns both within and between treatments decreased markedly as temperature increased, suggesting that higher temperatures promote more consistent individual consumption behaviors. Grasshoppers grew faster and larger as temperature increased, which translated into higher survival rates at higher temperatures. Warmer grasshoppers also did not alter their metabolic rates in response to predation risk cues, in contrast to colder grasshoppers. Digestive efficiency increased with temperature as well -- further indicating that lower temperatures were much more stressful than higher temperatures for grasshoppers. The study shows that physiological responses of ectothermic herbivores to predation stress are highly plastic and temperature dependent, with higher temperatures promoting increased protein intake, growth, development, survival, and digestive efficiency relative to colder temperatures. These findings help to reconcile why dietary responses (proportion of protein vs. carbohydrate intake) to predation stress may vary among different prey taxa studied previously.

Factors affecting individual foraging specialization and temporal diet stability across the range of a large "generalist" apex predator.

Individual niche specialization (INS) is increasingly recognized as an important component of ecological and evolutionary dynamics. However, most studies that have investigated INS have focused on the effects of niche width and inter- and intraspecific competition on INS in small-bodied species for short time periods, with less attention paid to INS in large-bodied reptilian predators and the effects of available prey types on INS. We investigated the prevalence, causes, and consequences of INS in foraging behaviors across different populations of American alligators (Alligator mississippiensis), the dominant aquatic apex predator across the southeast US, using stomach contents and stable isotopes. Gut contents revealed that, over the short term, although alligator populations occupied wide ranges of the INS spectrum, general patterns were apparent. Alligator populations inhabiting lakes exhibited lower INS than coastal populations, likely driven by variation in habitat type and available prey types. Stable isotopes revealed that over longer time spans alligators exhibited remarkably consistent use of variable mixtures of carbon pools (e.g., marine and freshwater food webs). We conclude that INS in large-bodied reptilian predator populations is likely affected by variation in available prey types and habitat heterogeneity, and that INS should be incorporated into management strategies to efficiently meet intended goals. Also, ecological models, which typically do not consider behavioral variability, should include INS to increase model realism and applicability.

The impact of complex chronic diseases on care utilization among assisted living residents.

PURPOSE: Many residents of assisted living (AL) have chronic diseases that are difficult to manage, including congestive heart failure (CHF), chronic obstructive pulmonary disease (COPD) and diabetes mellitus (DM). We estimated the amount and intensity of care delivered by the staff for residents with these conditions. METHODS: We performed a secondary data analysis from the Maryland Assisted Living (MDAL) Study (399 residents, 29 facilities). In-person assessments included measures of cognition, function, depression, and general medical health. Diagnosis of CHF, COPD, and DM, as well as current medications was abstracted from AL medical charts. Measures of care utilization were operationalized at the resident level as: 1) minutes per day of direct care (caregiver activity scale [CAS]), 2) subjective staff ratings of care burden, and 3) assigned AL "level of care" (based on state regulatory criteria). RESULTS: In best fit regression models, CHF and DM were not significant predictors of the evaluated care utilization measures; however, COPD was independently associated with increased minutes per day of direct care - 34% of the variance in the caregiver activity scale was explained by degree of functional dependency, cognitive impairment, age, and presence of COPD. Functional dependency, depressive symptoms, and age explained almost a quarter (23%) of the variance of staff care burden rating. For the AL level of care intensity rating, degree of functional dependency, level of cognition, and age were significant correlates, together explaining about 28% of the variance. CONCLUSION: The presence of COPD was a significant predictor of time per day of direct care. However, CHF and DM were not correlates of care utilization measures. Functional and cognitive impairment was associated with measures of care utilization, reiterating the importance of these characteristics in the utilization and intensity of care consumed by AL residents. Further study of this population could reveal other forms and amounts of care utilization.

Cohort differences in dementia recognition and treatment indicators among assisted living residents in Maryland: did a change in the resident assessment tool make a difference?

BACKGROUND: There is a lack of empirical evidence about the impact of regulations on dementia care quality in assisted living (AL). We examined cohort differences in dementia recognition and treatment indicators between two cohorts of AL residents with dementia, evaluated prior to and following a dementia-related policy modification to more adequately assess memory and behavioral problems. METHODS: Cross-sectional comparison of two AL resident cohorts was done (Cohort 1 [evaluated 2001-2003] and Cohort 2 [evaluated 2004-2006]) from the Maryland Assisted Living studies. Initial in-person evaluations of residents with dementia (n = 248) were performed from a random sample of 28 AL facilities in Maryland (physician examination, clinical characteristics, and staff and family recognition of dementia included). Adequacy of dementia workup and treatment was rated by an expert consensus panel. RESULTS: Staff recognition of dementia was better in Cohort 1 than in Cohort 2 (77% vs. 63%, p = 0.011), with no significant differences in family recognition (86% vs. 85%, p = 0.680), or complete treatment ratings (52% vs. 64%, p = 0.060). In adjusted logistic regression, cognitive impairment and neuropsychiatric symptoms correlated with staff recognition; and cognitive impairment correlated with family recognition. Increased age and cognitive impairment reduced odds of having a complete dementia workup. Odds of having complete dementia treatment was reduced by age and having more depressive symptoms. Cohort was not predictive of dementia recognition or treatment indicators in adjusted models. CONCLUSIONS: We noted few cohort differences in dementia care indicators after accounting for covariates, and concluded that rates of dementia recognition and treatment did not appear to change much organically following the policy modifications.

12-month incidence, prevalence, persistence, and treatment of mental disorders among individuals recently admitted to assisted living facilities in Maryland.

BACKGROUND: To estimate the 12-month incidence, prevalence, and persistence of mental disorders among recently admitted assisted living (AL) residents and to describe the recognition and treatment of these disorders. METHODS: Two hundred recently admitted AL residents in 21 randomly selected AL facilities in Maryland received comprehensive physician-based cognitive and neuropsychiatric evaluations at baseline and 12 months later. An expert consensus panel adjudicated psychiatric diagnoses (using DSM-IV-TR criteria) and completeness of workup and treatment. Incidence, prevalence, and persistence were derived from the panel's assessment. Family and direct care staff recognition of mental disorders was also assessed. RESULTS: At baseline, three-quarters suffered from a cognitive disorder (56% dementia, 19% Cognitive Disorders Not Otherwise Specified) and 15% from an active non-cognitive mental disorder. Twelve-month incidence rates for dementia and non-cognitive psychiatric disorders were 17% and 3% respectively, and persistence rates were 89% and 41% respectively. Staff recognition rates for persistent dementias increased over the 12-month period but 25% of cases were still unrecognized at 12 months. Treatment was complete at 12 months for 71% of persistent dementia cases and 43% of persistent non-cognitive psychiatric disorder cases. CONCLUSIONS: Individuals recently admitted to AL are at high risk for having or developing mental disorders and a high proportion of cases, both persistent and incident, go unrecognized or untreated. Routine dementia and psychiatric screening and reassessment should be considered a standard care practice. Further study is needed to determine the longitudinal impact of psychiatric care on resident outcomes and use of facility resources.

Childless Elders in Assisted Living: Findings from the Maryland Assisted Living Study.

We compared data drawn from a random sample of 399 current assisted living (AL) residents and a subsample of 222 newly admitted residents for two groups: childless AL residents and AL residents with children. The percentage of childless AL residents (26%) in our study was slightly higher than US population estimates of childless persons age 65 and over (20%). In the overall sample, the two groups differed significantly by age, race and women's years of education. The childless group was slightly younger, had a higher percentage of African American residents, and had more years of education than the group with children. In the subsample, we looked at demographic, functional, financial and social characteristics and found that compared to residents with children, fewer childless residents had a dementia diagnosis, received visits from a relative while more paid less money per month for AL and reported having private insurance. As childlessness among older adults continues to increase, it will become increasingly important to understand how child status affects the need for and experience of long-term care.

Golf course living leads to a diet shift for American alligators.

Human-driven land use change can fundamentally alter ecological communities, especially the diversity and abundance of large-bodied predators. Yet, despite the important roles large-bodied predators play in structuring communities through feeding, there have been only a few investigations of how the feeding patterns of large-bodied predators change in human-dominated landscapes. One group of large-bodied predators that has been largely overlooked in the context of land use change is the crocodilians. To help fill these gaps, we studied the feeding patterns of juvenile American alligators (Alligator mississippiensis) on neighboring barrier islands on the southeast coast of Georgia, USA. Jekyll Island has multiple golf courses and substantial amounts of human activity, while Sapelo Island does not have any golf courses and a much smaller amount of human activity. We found that juvenile alligator populations on both islands ate the same types of prey but in vastly different quantities. Sapelo Island alligators primarily consumed crustaceans while alligators that lived on Jekyll Island's golf courses ate mostly insects/arachnids. Furthermore, the Jekyll Island alligators exhibited a much more generalist feeding pattern (individuals mostly ate the same types of prey in the same quantities) than the more specialized Sapelo Island alligators (diets were more varied across individuals). The most likely explanation for our results is that alligators living on golf courses have different habitat use patterns and have access to different prey communities relative to alligators in more natural habitats. Thus, land use change can strongly alter the feeding patterns of large-bodied predators and, as a result, may affect their body condition, exposure to human-made chemicals, and role within ecological communities.

Age, CAG repeat length, and clinical progression in Huntington's disease.

The objective of this study was to further explore the effect of CAG repeat length on the rate of clinical progression in patients with Huntington's disease. The dataset included records for 569 subjects followed prospectively at the Baltimore Huntington's Disease Center. Participants were seen for a mean of 7.1 visits, with a mean follow-up of 8.2 years. Subjects were evaluated using the Quantified Neurologic Examination and its Motor Impairment subscale, the Mini-Mental State Examination, and the Huntington's disease Activities of Daily Living Scale. By itself, CAG repeat length showed a statistically significant but small effect on the progression of all clinical measures. Contrary to our previous expectations, controlling for age of onset increased the correlation between CAG repeat length and progression of all variables by 69% to 159%. Graphical models further supported the idea that individuals with smaller triplet expansions experience a more gradual decline. CAG repeat length becomes an important determinant of clinical prognosis when accounting for age of onset. This suggests that the aging process itself influences clinical outcomes in Huntington's disease. Inconsistent results in prior studies examining CAG repeat length and progression may indeed reflect a lack of age adjustment.

Striatal neuronal loss correlates with clinical motor impairment in Huntington's disease.

Huntington's disease (HD) is characterized clinically by chorea, motor impairment, psychiatric manifestations, and dementia. Atrophy of the striatum is the neuropathological hallmark of HD, and previous studies have suggested that striatal atrophy correlates more closely with motor impairment than with chorea. Motor impairment, as measured by motor impairment score, correlates with functional disability in HD patients, but chorea does not. In this study, we investigated the relation between neuronal loss and these motor features. We conducted neuropathological and stereologic assessments of neurons in putamen and subthalamic nuclei in HD patients and age-matched controls. In putamen, we estimated the total number and volume of medium spiny neurons labeled with dopamine- and cAMP-regulated phosphoprotein 32 kDa (DARPP-32). In subthalamic nuclei, we estimated the total number of neurons on hematoxylin & eosin/luxol fast blue stains. In putamen of HD, immunohistochemistry showed DARPP-32 neuronal atrophy with extensive disruption of neurites and neuropil; stereologic studies found significant decreases in both the number and size of DARPP-32 neurons; we also detected a significant reduction of overall putamen volume in HD patients, compared to controls. In subthalamic nuclei, there was a mild, but significant, neuronal loss in the HD group. The loss of neurons in putamen and subthalamic nuclei as well as putaminal atrophy were significantly correlated with severity of motor impairment, but not with chorea. Our findings suggest that neuronal loss and atrophy in striatum and neuronal loss in subthalamic nuclei contribute specifically to the motor impairment of HD, but not to chorea.

Seizures in juvenile Huntington's disease: frequency and characterization in a multicenter cohort.

Little is known about the epilepsy that often occurs in the juvenile form of Huntington's disease (HD), but is absent from the adult-onset form. The primary aim of this study was to characterize the seizures in juvenile HD (JHD) subjects with regard to frequency, semiology, defining EEG characteristics, and response to antiepileptic agents. A multicenter, retrospective cohort was identified by database query and/or chart review. Data on age of HD onset, primary HD manifestations, number of CAG repeats, the presence or absence of seizures, seizure type(s), antiepileptic drugs used, subjects' response to antiepileptic drugs (AEDs), and EEG results were assembled, where available. Ninety subjects with genetically confirmed JHD were included. Seizures were present in 38% of subjects and were more likely to occur with younger ages of HD onset. Generalized tonic-clonic seizures were the most common seizure type, followed by tonic, myoclonic, and staring spells. Multiple seizure types commonly occurred within the same individual. Data on EEG findings and AED usage are presented. Seizure risk in JHD increases with younger age of HD onset. Our ability to draw firm conclusions about defining EEG characteristics and response to AEDs was limited by the retrospective nature of the study. Future prospective studies are required.

Factors contributing to institutionalization in patients with Huntington's disease.

The objective of this study was to determine which factors are predictive of institutionalization in Huntington's disease. Seven hundred and ninety-nine subjects with 4313 examinations from the Baltimore Huntington's Disease Center were included in the data set; 88 of these patients with an average follow-up time of 9.2 years went from living at home to being institutionalized while being observed in our clinic. We examined demographic, genetic, and clinical variables for a relationship with institutionalization using linear regressions, a Cox proportional hazards model, and χ2 or t tests in certain cases. In our linear models, scores on the Quantified Neurologic Examination (R2=0.203, P<.001), Huntington's disease Activities of Daily Living Scale (R2=0.259, P<.001), and Motor Impairment Score (R2=0.173, P<.001) were found to have the strongest correlation with time until institutionalization. In addition, CAG repeat length (R2=0.248, P<.001) was significantly associated with disease duration at institutionalization, when controlling for age at onset. In the Cox proportional hazards model, scores on the Activities of Daily Living Scale, Mini-Mental State Examination, Quantified Neurologic Examination, and Motor Impairment Score all significantly predicted placement in long-term care. Finally, institutionalized patients were shown to have a higher CAG number and a lower level of educational attainment than patients who avoided institutionalization for at least 15 years after disease onset. Neurologic findings, functional capacity, cognitive impairment, and CAG repeat length are all likely determinants of institutionalization. In contrast with other dementing conditions like Parkinson's and Alzheimer's, psychiatric symptoms were not shown to predict institutionalization in Huntington's disease. This may illustrate the especially debilitating nature of the movement disorder of Huntington's disease in comparison with the other dementias.

Does variation in movement tactics and trophic interactions among American alligators create habitat linkages?

1. Highly mobile top predators are hypothesized to spatially and/or temporally link disparate habitats through the combination of their movement and feeding patterns, but recent studies suggest that individual specialization in habitat use and feeding could keep habitats compartmentalized. 2. We used passive acoustic telemetry and stable isotope analysis to investigate whether specialization in movement and feeding patterns of American alligators (Alligator mississippiensis) in an oligotrophic subtropical estuary created habitat linkages between marine and estuarine/freshwater food webs. 3. Individual alligators adopted one of the three relatively distinct movement tactics that were linked to variation in diets. Fifty-six per cent of alligators regularly travelled from the upstream (freshwater/mid-estuary) areas into the downstream (marine-influenced) areas where salinities exceed those typically tolerated by alligators. Thirty-one per cent of the alligators made regular trips from the mid-estuarine habitat into the upstream habitat; 13% remained in the mid-estuary zone year-round. 4. Stable isotopic analysis indicated that, unlike individuals remaining in the mid-estuary and upstream zones, alligators that used the downstream zone fed at least partially from marine food webs and likely moved to access higher prey abundance at the expense of salt stress. Therefore, 'commuting' alligators may link marine food webs with those of the estuary and marshes in the coastal Everglades and create an upstream vector for allochthonous nutrient inputs into the estuary. 5. This study lends further support to the hypothesis that large-bodied highly mobile predators faced with trade-offs are likely to exhibit individual specialization leading to habitat linkages, rather than compartmentalization. However, the conditions under which this scenario occurs require further investigation.

A Descriptive Study of Home Modifications for People with Dementia and Barriers to Implementation.

This study describes home environmental features, safety issues, and health-related modifications in a community dwelling sample of 82 elderly people with dementia. Main barriers to the accessibility of the homes were steps, both inside and outside the house. The majority of the caregivers had made home modifications, which pertained mainly to physical limitations. Home modifications to support cognitive deficits were made to a lesser extent. The main barrier to the implementation of home modifications to accommodate the care recipient's memory loss was skepticism about their usefulness. Regarding the removal of physical barriers, financial constraints were most frequently mentioned.

The physical environment influences neuropsychiatric symptoms and other outcomes in assisted living residents.

OBJECTIVE: Although the number of elderly residents living in assisted living (AL) facilities is rising, few studies have examined the AL physical environment and its impact on resident well-being. We sought to quantify the relationship of AL physical environment with resident outcomes including neuropsychiatric symptoms (NPS), quality of life (QOL), and fall risk, and to compare the effects for demented and non-demented residents. METHODS: Prospective cohort study of a stratified random sample of 326 AL residents living in 21 AL facilities. Measures included the Therapeutic Environmental Screening Scale for Nursing Homes and Residential Care (TESS-NH/RC) to rate facilities and in-person assessment of residents for diagnosis (and assessment of treatment) of dementia, ratings on standardized clinical, cognitive, and QOL measures. Regression models compared environmental measures with outcomes. TESS-NH/RC is modified into a scale for rating the AL physical environment AL-EQS. RESULTS: The AL Environmental Quality Score (AL-EQS) was strongly negatively associated with Neuropsychiatric Inventory (NPI) total score (p < 0.001), positively associated with Alzheimer Disease Related Quality of Life (ADRQL) score (p = 0.010), and negatively correlated with fall risk (p = 0.042). Factor analysis revealed an excellent two-factor solution, Dignity and Sensory. Both were strongly associated with NPI and associated with ADRQL. CONCLUSION: The physical environment of AL facilities likely affects NPS and QOL in AL residents, and the effect may be stronger for residents without dementia than for residents with dementia. Environmental manipulations that increase resident privacy, as well as implementing call buttons and telephones, may improve resident well-being.

Alligators in the big city: spatial ecology of American alligators (Alligator mississippiensis) at multiple scales across an urban landscape.

Urbanization impacts wildlife, yet research has been limited to few taxa. American alligators (Alligator mississippiensis) are apex predators that have received minimal attention within urban areas. We investigated potential effects of urban land use on alligators through surveys of relative alligator abundance in nine tributaries of the lower St. Johns River within Jacksonville, FL. We then explored the potential effects of urban development on alligator spatial distribution and habitat selection at coarse and fine scales. At the coarse scale, we found no correlation between percent developed land and alligator abundance across tributaries; instead, salinity was the primary driver. However, at the fine scale alligators preferred habitats with more open water and vegetated shorelines and avoided anthropogenic structure. Surprisingly, only one of 93 sighted individuals was an adult. Hunting and nuisance alligator data suggests that adults are relatively rare in Jacksonville because they have been targeted for removal. Thus, smaller alligators still occupy urban habitats because they are not targeted and face no competition from adults. Increasing urbanization and human activity may further degrade alligator habitats and limit the distribution of breeding adults, potentially leading to local population declines.