Variable sex-specific mortality due to shorebird predation on a fiddler crab

2003 ◽  
Vol 81 (7) ◽  
pp. 1209-1221 ◽  
Author(s):  
Pablo D Ribeiro ◽  
Oscar O Iribarne ◽  
Luciano Jaureguy ◽  
Diego Navarro ◽  
Eugenia Bogazzi
Keyword(s):  
Sex Ratio ◽  
Fiddler Crab ◽  
Dry Mass ◽  
High Density ◽  
Migratory Shorebirds ◽  
Specific Mortality ◽  
Crab Density ◽  
Feeding Activities ◽  
Golden Plover ◽  
Uca Uruguayensis

Male fiddler crabs compete for access to mates mainly by displaying an enlarged claw. One cost of this large claw is presumed to be higher exposure to predators. The fiddler crab Uca uruguayensis is used as a food source by several Neotropical migratory shorebirds. We investigated whether crab density and male claw-waving behaviour increase predation by shorebirds. The sex ratio of crabs on the surface was strongly male biased. Male crabs showed a daily succession of feeding–waving–feeding activities and their dry mass at the site decreased with a high density of crabs, suggesting stronger male–male competition than at sites with a low density of crabs. Sex-specific predation varied according to shorebird species. The Ruddy Turnstone (Arenaria interpres) preyed intensively on male crabs when they were courting and at sites with a high density of crabs, the Black-bellied Plover (Pluvialis squatarola) and the Lesser Golden Plover (Pluvialis dominica) preyed on crabs of both sexes, and the Whimbrel (Numenius phaeopus) foraged intensively on females. When estimating the net effect of all predators, we found that the four shorebird species together were able to consume between 0.1 and 0.2% of the crab population, and consumption did not differ between the sexes of crabs. These mortality rates indicate a low source of mortality, likely unable to produce deviations in the sex ratio of the population. Thus, our results indicate that a trait thought to be sexually selected does not necessarily lead to a disproportionate increase in mortality due to predation.

‘Photography’ as a useful method for estimating the density, sex-ratio and body size of the surface-active Austruca perplexa (H. Milne Edwards, 1852) (Brachyura, Ocypodidae)

Crustaceana ◽  
2021 ◽  
Vol 94 (11-12) ◽  
pp. 1429-1440
Author(s):  
Kanitta Keeratipattarakarn ◽  
Fahmida Wazed Tina ◽  
Rattapon Sangngam ◽  
Ketsanee Thongsri ◽  
Arreeya Suphap
Keyword(s):  
Body Size ◽  
Sex Ratio ◽  
Fiddler Crab ◽  
Body Sizes ◽  
Crab Density ◽  
Surface Active ◽  
Non Destructive ◽  
Photography Method

Abstract Estimations of crab density, sex-ratio, and body sizes are difficult. Though the ‘burrow excavation’ method is widely used to estimate these parameters in surface-active crabs, it is destructive to crab populations. Therefore, an alternative, non-destructive method is desirable. This study compared the non-destructive ‘photography’ method with the ‘burrow excavation’ method in a fiddler crab (Austruca perplexa (H. Milne Edwards, 1852)) population. Twenty 0.25 m2 quadrats were set out and 4 photos were taken of the surface-active crabs in each quadrat. All crab burrows were then excavated, and the crabs were collected to estimate their numbers, sexes, and body and claw sizes. Afterward, the photographs were analysed to estimate the same parameters by using the GIMP program. These parameters were then compared between the two methods. The results showed that these parameters were not different between the methods compared. This study thus reveals that the ‘photography’ method could safely be used instead of the ‘burrow excavation’ method, and yield the same results.

Agonistic interactions in the male fiddler crab Uca leptodactyla Rathbun, 1898 at varying densities

Crustaceana ◽  
2015 ◽  
Vol 88 (6) ◽  
pp. 625-640 ◽  
Author(s):  
L. C. Santos ◽  
C. E. R. D. Alencar ◽  
F. A. M. Freire ◽  
A. C. Luchiari
Keyword(s):  
Population Density ◽  
Mangrove Forest ◽  
Fiddler Crab ◽  
High Density ◽  
Agonistic Behaviour ◽  
Agonistic Interactions ◽  
Energy Investment ◽  
Low Level ◽  
Crab Density ◽  
Interaction Intensity

In this study we tested the effect of population density on agonistic interactions in male Uca leptodactyla Rathbun, 1898. We recorded the crab’s behaviour in pairs or in groups of five animals composed of conspecifics and heterospecifics living in the same area (sympatric) and distinct areas (allopatric) of the mangrove forest. Allopatric conspecific crabs showed higher approaching and signalling than those in other conditions. The higher the crab density, the lower the interaction intensity between animals. Low-level agonistic signals were mainly displayed in high density (groups), while claw touch mainly occurred in pairs. Allopatric conspecifics showed the more intense agonistic interactions. Therefore, Uca seems to decrease energy investment in unnecessary fights against sympatric and conspecific crabs. Population density is a major factor driving agonistic behaviour mainly when conspecific animals are kept together. This may occur due to the increased competition for the same resources.

The fiddler crab, Uca bengali Crane, 1975: population biology and burrow characteristics on a riverbank in southern Thailand

Crustaceana ◽  
2015 ◽  
Vol 88 (7-8) ◽  
pp. 791-807 ◽  
Author(s):  
Fahmida Wazed Tina ◽  
Mullica Jaroensutasinee ◽  
Onprang Sutthakiet ◽  
Krisanadej Jaroensutasinee
Keyword(s):  
Organic Matter ◽  
Body Size ◽  
Sex Ratio ◽  
Moisture Content ◽  
Population Biology ◽  
Fiddler Crab ◽  
Tidal River ◽  
Southern Thailand ◽  
Percent Moisture ◽  
Crab Density

We studied the population structure ofUca bengaliCrane, 1975 (crab density, sex ratio, and body size (i.e., carapace length and width, major claw length and width)), along with burrow characteristics (diameter, length, depth, and volume) as well as sediment characteristics (percent moisture content and organic matter) along a bank gradient at three distances (2, 4 and 6 m) from the edge of a tidal river. The results showed no differences in crab density, sex ratio, and body size among the three distances. The percent moisture content at 2 m distance was higher than at 4 and 6 m, and the percentage organic matter at 2 m distance was higher than at 6 m distance. Burrows were shorter in length, shallower in depth, and smaller in volume at 2 m distance, but these measures increased with increasing distance from the river edge. Both males and females made three distinct burrow shapes: I, J and U; the J-shaped burrows were the most numerous at all distances.

scholarly journals Evaluating the potential impact of bird predation on the SW Atlantic fiddler crab Leptuca uruguayensis

2019 ◽  
Vol 73 (1) ◽  
Author(s):  
Pablo D. Ribeiro ◽  
Diego D. Navarro ◽  
Luciano M. Jaureguy ◽  
Pedro Daleo ◽  
Oscar O. Iribarne
Keyword(s):  
Field Data ◽  
Fiddler Crab ◽  
Bird Species ◽  
Simulation Methods ◽  
Bird Predation ◽  
Feeding Site ◽  
Bird Density ◽  
Crab Density ◽  
Sw Atlantic ◽  
Potential Impact

Abstract The southernmost permanent population of the fiddler crab Leptuca uruguayensis occurs along the Samborombón Bay (36°22′S, 56°45′W, Argentina), an important feeding site for many bird species, including ruddy turnstones (Arenaria interpres), whimbrels (Numenius phaeopus), grey plovers (Pluvialis squatarola), american golden plovers (Pluvialis dominica) and gull-billed terns (Gelochelidon nilotica). Although all these birds are known to prey on many fiddler crab species worldwide, there is no estimation of their joint predation impacts, probably due to the difficulty in conducting experiments on an appropriate spatial scale. In these situations, computer simulation methods are useful tools. By using Monte Carlo methods and field data, we modeled the decrease of a fiddler crab population due to bird predation. The model found that under current bird occurrences and crab densities, birds do not consume more than 0.03% of the studied fiddler crab populations. Birds only consume more than 10% of the population if crab density is below 0.02 crabs m2, or if bird occurrences are at least 3 orders of magnitude higher than currently observed. Both situations are unlikely, as mean crab density is 140 crabs m2, and bird density is never so high. Furthermore, by monitoring three different fiddler crab patches, we found that bird predation cannot account for temporal density changes, suggesting that other population processes are more important than bird predation. In conclusion, even though fiddler crabs may exhibit strong predator-avoidance behavior, direct lethal effects of bird predation are currently small.

Effects of population density on female and male burrow characteristics in the fiddler crab, Uca bengali Crane, 1975

Crustaceana ◽  
2015 ◽  
Vol 88 (12-14) ◽  
pp. 1283-1299 ◽  
Author(s):  
Fahmida Wazed Tina ◽  
Mullica Jaroensutasinee ◽  
Krisanadej Jaroensutasinee
Keyword(s):  
Body Size ◽  
Population Density ◽  
Fiddler Crab ◽  
High Density ◽  
The Other ◽  
Low Density ◽  
Density Effects ◽  
Egg Incubation ◽  
Other Hand ◽  
Males And Females

We examined the effects of population density on body size and burrow characteristics ofUca bengaliCrane, 1975. We predicted that (1) males in high-density areas (HD) should be larger in size and build higher quality burrows than males in low-density areas (LD), and (2) HD females should be larger in size, but build lower quality burrows than LD females, as HD females can find higher numbers of good quality male burrows around them for breeding and egg incubation. Our results showed that males and females in HD were larger in size than those in LD. Since HD males were larger in size, they built higher quality burrows than males in LD. On the other hand, even though LD females were smaller in size than HD ones, they built higher quality burrows than HD females. Our results thus indicate that density effects both body size and burrow characteristics.

Demography of Eurotestudo hermanni in a mesic area of Central Italy

2007 ◽  
Vol 28 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Valeria Ramacciato ◽  
Massimo Capula ◽  
Anna Loy ◽  
Federica Gentilotti
Keyword(s):  
Sex Ratio ◽  
Central Italy ◽  
Average Density ◽  
High Density ◽  
Environmental Constraints ◽  
Adult Males ◽  
Males And Females ◽  
European Populations

AbstractHermann's tortoise (Eurotestudo hermanni) from a mesic area of Central Italy (Isernia, Molise) was investigated during a two-year period (2003-2004). The population is characterized by a fairly high density when compared to other Italian and European populations, with density ranging from 16.16 individuals/ha in 2003 to 25.08 individuals/ha in 2004 (average density 20.84/ha). The sex ratio was 1:1 both in 2003 and 2004. Females were captured in higher percentages from May to July in both years, while males were most abundant from August to October. These differences can be related to the different needs and behaviour of males and females in the two periods, and to the environmental constraints of the study area. All the marked tortoises were found aged between 10 and 21 years. Adult males and females from the study area were small-sized when compared to those from other Italian and European populations.

scholarly journals Male-specific mortality biases secondary sex ratio in Eurasian tree sparrowsPasser montanus

2017 ◽  
Vol 7 (24) ◽  
pp. 10675-10682
Author(s):  
Takahiro Kato ◽  
Shin Matsui ◽  
Yohey Terai ◽  
Hideyuki Tanabe ◽  
Sayaka Hashima ◽  
...  
Keyword(s):  
Sex Ratio ◽  
Specific Mortality ◽  
Secondary Sex Ratio ◽  
Male Specific
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