Isotopic niche partitioning in two sympatric howler monkey species.

OBJECTIVES: Ecological similarity between species can lead to interspecific trophic competition. However, when ecologically similar species coexist, they may differ in foraging strategies and habitat use, which can lead to niche partitioning. As the body tissues of consumers contain a stable isotope signature that reflects the isotopic composition of their diet, stable isotope analysis is a useful tool to study feeding behavior. We measured the isotopic niche width, which is a proxy for trophic niche width, of mantled (Alouatta palliata) and black (A. pigra) howler monkeys. Specifically, studied populations in allopatry and sympatry to assess whether these species showed niche partitioning. MATERIALS AND METHODS: Between 2008 and 2012, we collected hair samples from 200 subjects (113 black and 87 mantled howler monkeys) and used continuous flow isotope ratio mass spectrometry to estimate δ13 C and δ15 N. We described the isotopic niche width of each species in allopatry and sympatry with the Bayesian estimation of the standard ellipse areas. RESULTS: In allopatry, isotopic niche width and isotopic variation were similar in both species. In sympatry, black howler monkeys had a significantly broader isotopic niche, which was mainly determined by high δ15 N values, and included the majority of mantled howler monkeys' isotopic niche. The isotopic niche of mantled howler monkeys did not differ between sympatry and allopatry. CONCLUSIONS: The coexistence of these ecologically similar species may be linked to trophic niche adjustments by one species, although the particular features of such adjustments (e.g., dietary, spatial, or sensory partitioning) remain to be addressed.

Isotopic niche partitioning between two apex predators over time.

Stable isotope analyses have become an important tool in reconstructing diets, analysing resource use patterns, elucidating trophic relations among predators and understanding the structure of food webs. Here, we use stable carbon and nitrogen isotope ratios in bone collagen to reconstruct and compare the isotopic niches of adult South American fur seals (Arctocephalus australis; n = 86) and sea lions (Otaria flavescens; n = 49) - two otariid species with marked morphological differences - in the Río de la Plata estuary (Argentina - Uruguay) and the adjacent Atlantic Ocean during the second half of the 20th century and the beginning of the 21st century. Samples from the middle Holocene (n = 7 fur seals and n = 5 sea lions) are also included in order to provide a reference point for characterizing resource partitioning before major anthropogenic modifications of the environment. We found that the South American fur seals and South American sea lions had distinct isotopic niches during the middle Holocene. Isotopic niche segregation was similar at the beginning of the second half of the 20th century, but has diminished over time. The progressive convergence of the isotopic niches of these two otariids during the second half of the 20th century and the beginning of the 21st century is most likely due to the increased reliance of South American fur seals on demersal prey. This recent dietary change in South American fur seals can be explained by at least two non-mutually exclusive mechanisms: (i) the decrease in the abundance of sympatric South American sea lions as a consequence of small colony size and high pup mortality resulting from commercial sealing; and (ii) the decrease in the average size of demersal fishes due to intense fishing of the larger class sizes, which may have increased their accessibility to those eared seals with a smaller mouth gape, that is, South American fur seals of both sexes and female South American sea lions.

Estimativas da qualidade de linhas poligonais topográficas / Quality estimations of topographical traverses

O objetivo deste artigo é descrever um procedimento que contribui com estimativas de qualidade de levantamento topográficos mediante a pré-análise e estimativas obtidas a partir de análise pós-ajustamento. As estimativas são dadas pelo teste qui-quadrado da forma quadrática do erro de fechamento, pelo teste qui-quadrado da forma quadrática dos resíduos obtidos no ajustamento pelo método dos mínimos quadrados, pelo teste data snooping de Baarda, pela elipse dos erros, pela elipse de confiança, pelo círculo do erro de posição e pelo círculo do erro médio. Estes conceitos são examinados por meio de valores numéricos no caso de uma linha poligonal simples implantada no campus da Universidade Federal de Santa Maria e medida com um taquímetro eletrônico.

The objective through this article is to describe a procedure that contributes with quality survey estimations by means pre-analysis survey and estimations by means post-adjustment. The estimations are given by the chi-square test of the quadratic form of misclosures, the chi-square of the quadratic form of residuals from the least-squares adjustment method, the Baarda's data snooping test, the standard ellipse, the confidence ellipse, position error circle and mean error circle. These concepts are examined through the numerical values provided in the case of a simple topographical traverse which was implanted at the Universidade Federal de Santa Maria Campus with electronic tachymeter.

Estimativas da qualidade de linhas poligonais topográficas

The objective through this article is to describe a procedure that contributes with quality survey estimations by means pre-analysis survey and estimations by means post-adjustment. The estimations are given by the chi-square test of the quadratic form of misclosures, the chi-square of the quadratic form of residuals from the least-squares adjustment method, the Baarda's data snooping test, the standard ellipse, the confidence ellipse, position error circle and mean error circle. These concepts are examined through the numerical values provided in the case of a simple topographical traverse which was implanted at the Universidade Federal de Santa Maria Campus with electronic tachymeter.

O objetivo deste artigo é descrever um procedimento que contribui com estimativas de qualidade de levantamento topográficos mediante a pré-análise e estimativas obtidas a partir de análise pós-ajustamento. As estimativas são dadas pelo teste qui-quadrado da forma quadrática do erro de fechamento, pelo teste qui-quadrado da forma quadrática dos resíduos obtidos no ajustamento pelo método dos mínimos quadrados, pelo teste data snooping de Baarda, pela elipse dos erros, pela elipse de confiança, pelo círculo do erro de posição e pelo círculo do erro médio. Estes conceitos são examinados por meio de valores numéricos no caso de uma linha poligonal simples implantada no campus da Universidade Federal de Santa Maria e medida com um taquímetro eletrônico.

Estimativas da qualidade de linhas poligonais topográficas

The objective through this article is to describe a procedure that contributes with quality survey estimations by means pre-analysis survey and estimations by means post-adjustment. The estimations are given by the chi-square test of the quadratic form of misclosures, the chi-square of the quadratic form of residuals from the least-squares adjustment method, the Baarda's data snooping test, the standard ellipse, the confidence ellipse, position error circle and mean error circle. These concepts are examined through the numerical values provided in the case of a simple topographical traverse which was implanted at the Universidade Federal de Santa Maria Campus with electronic tachymeter.

O objetivo deste artigo é descrever um procedimento que contribui com estimativas de qualidade de levantamento topográficos mediante a pré-análise e estimativas obtidas a partir de análise pós-ajustamento. As estimativas são dadas pelo teste qui-quadrado da forma quadrática do erro de fechamento, pelo teste qui-quadrado da forma quadrática dos resíduos obtidos no ajustamento pelo método dos mínimos quadrados, pelo teste data snooping de Baarda, pela elipse dos erros, pela elipse de confiança, pelo círculo do erro de posição e pelo círculo do erro médio. Estes conceitos são examinados por meio de valores numéricos no caso de uma linha poligonal simples implantada no campus da Universidade Federal de Santa Maria e medida com um taquímetro eletrônico.