科研之友
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摘要
For nine days, the number of sally lightfoot crabs (Grapsus grapsus) in a 300 m2 area within the brown booby (Sula leucogaster) colony and the activity of each crab were recorded in the morning (5:30-7:30 h), at midday (11:30-13:30 h), and in the afternoon (15:30-17:30 h). The average number of individuals was 80.2 ㊣15.5 (59-111) in the morning, 3.1 ㊣ 2.3 (0-7) at midday, and 65.3 ㊣ 15 (49-92) in the afternoon. A total of 1338 activity records were made, with the crabs standing still or walking in 844 records and handling material or feeding in 494 records. In the latter records, 53% of the crabs were handling detritus (pieces of dry bird excrement and sediment), 12.2% were handling feathers, 12.8% were feeding on regurgitated fish, 8.9% were feeding on dead Sula leucogaster, 8.1% were feeding on crab, 4.7% were feeding on material adhered to egg shells, and 0.6% were feeding on live nestlings of S. leucogaster. The low frequency of crabs in the colony around noon shows that the crabs avoid insolation, hiding in shady places and tidal pools. In the Sao Pedro and Sao Paulo Archipelago, the presence of S. leucogaster represents an important food source for G. grapsus. This crab plays the role of a cleaner in the S. leucogaster colony, consuming food remains, broken eggs, and dead birds Durante nueve d赤as se registr車 el n迆mero de cangrejos costeros (Grapsus grapsus) en una 芍rea de 300 m2dentro de la colonia de piquero caf谷 (Sula leucogaster) y la actividad de cada uno de los individuos durante la ma ana (5:30-7:30 h), mediod赤a (11:30-13:30 h) y tarde (15:30-17:30 h). La media de individuos en la ma ana fue 80,2 ㊣ 15,5 (59-111), en el mediod赤a 3,1 ㊣ 2,3 (0-7) y en la tarde 65,3 ㊣ 15 (49-92). Del total de 1.338 registros de comportamiento, 844 fueron de cangrejos detenidos o caminando y 494 manipulando alg迆n material o alimento. De 谷stos, 53% fueron de manipulaci車n de detrito (excremento seco de ave y sedimento); 12,2% de manipulaci車n de plumas; 12,8% aliment芍ndose de peces regurgitados; 8,9% de un Sula muerto; 8,1% de cangrejo; 4,7% de material adherido a las cascaras de huevos y 0,6% de cr赤a de Sula viva. La baja frecuencia de los cangrejos en la colonia durante el mediod赤a es una evidencia que los mismos se protegen de la insolaci車n, permaneciendo en la sombra y en pozas de marea. En el archipi谷lago de Sao Pedro y Sao Paulo la presencia de S. leucogaster representa una importante fuente de alimentaci車n para G. grapsus, que desempe a un papel de limpiador en la colonia de esta ave, consumiendo restos de comida, huevos quebrados y aves muertas
