It is fundamentally approved your location, attendance, and you will shelter of colony could be the chief issues one to influence this new viability out-of egg while the rate out-of colony predation ( Arnold ainsi que al. 1987, Martin 1995, Cresswell 1997). Constancy while in the incubation provides a great thermal ecosystem to the development out of embryos and protects egg out of significant temperature that’ll affect its hatchability ( Offer 1982). Inside variety where just one sex incubates, there clearly was a swap-from anywhere between attendance and you may cover of colony and you can fix regarding a good opportunity harmony ( Thompson and you can Ravelin 1987, Flint and you may Grand 1999). As well, colony notice can be reduce the threat of egg predation possibly from the energetic nest safety otherwise down seriously to a reduced total of the incubation period of egg, and this a reduced amount of big date he could be met with predators ( Clutton-Brock 1991, Creswell 1997, Flint and you can Huge 1999).
Tips
Within the Greater Rheas (Rhea americana), adult proper care is accomplished solely by guys, that have lady limiting the money into development and laying off eggs. Rhea men make the latest nest, incubate this new eggs, and you will look after the chicks after hatching ( Muniz 1885, Bruning 1974, Fernandez and you can Reboreda 1998). Where variety, new mating program integrates harem polygyny and you will sequential polyandry ( Muniz 1885, Bruning 1974). Early in the latest reproduction 12 months (August–September) men participate to have, and guard a team or harem of five so you’re able to eight women. The male copulates towards the people at least once all the a couple of to three weeks. Female put egg all forty-eight h for 10–twelve weeks during the a communal colony ( Bruning 1974, Fernandez and you will Reboreda 1998). Chicks hatch synchronously in addition to their care is accomplished only because of the men ( Bruning 1974, Fernandez and you will Reboreda 1998). After the lady finish the putting for the first male they can copulate and you will set egg for another male ( Muniz 1885, Bruning 1974).
Here, i evaluated the fresh the total amount of Better Rhea men parental proper care while in the egg and chick values. I measured nest attract by men and its particular impact on brand new viability and you may emergency regarding egg. We tested whether male absences when you look at the incubation was timed so you can stop embryos getting life-threatening temperature throughout development, or even reduce the risk of egg predation. I analyzed the result off nest attention towards the viability of brand new eggs by contrasting heat off egg the whole day inside nests that have and you can instead men appeal. Similarly, i analyzed effectation of male care and attention to your probability of eggs predation of the contrasting the fresh survival off eggs in the nests which have and you will without men worry. Simultaneously, i examined the the total amount out-of adult care once hatching and you can examined their relative rates by evaluating the amount of time allocated to eating and you can vigilance because of the guys having chicks, nonreproductive single men and you will males for the nonreproductive organizations.
Studies area
The research is actually held inside reproduction (August–January) and nonbreeding (January–July) seasons out-of 1993–1997, in two spatially contiguous cattle ranches regarding 3,five-hundred and 800 ha. Those ranches was basically receive around the town of General Lavalle during the the brand new state from Buenos Aires, Argentina (36°25’S, 56°56’W). A people from ?eight hundred rheas are managed thereon studies area, with a beneficial sex proportion biased slightly toward men (55% men and you may forty five% females). The research area was a temperate grassland as part of the very-called flood pampa ( Soriano 1991). The bedroom are flat, reduced, and you can marshy, with little to no of your land rising >10 m above sea level. Local herbs is made from short grass species which have scattered spots out of forest from the high areas. One to area is used nearly only for cattle husbandry but still features several insane communities of Greater Rheas. Within analysis web site, adult rheas lack sheer predators today (i.age. cougars [Felis concolor]) but Crested Caracara (Polyborus plancus), Chimango Caracara (Milvago chimango), grey foxes (Dusicyon kvinner Europeisk gymnocercus), grisons (Galictis sp.), and you can opossums (Didelphis albiventris) sufferer greatly on rhea chicks. Most other low-indigenous predators that will attack each other grownups and you can chicks try feral animals (Meters. Beade pers. obs.) but i have no research you to definitely that kind of predation got taken place from inside the data several months.