Diet of Greater Rheas in an Agroecosystem of Central Argentina

Martella, Mónica B.; Navarro, Joaquín L.; Gonnet, Jorge M.; Monge, Susana

doi:10.2307/3802076

Cited by 50 publications

(64 citation statements)

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“…Orientations of muscles were estimated in lateral radiograms from the known position of origo and insertio of the muscles. The lower jaw articulates around the quadrato-mandibular articulation and is in its rest position in all calculations, which is in agreement with the situation when feeding on green plant material, comprising 90% of the natural diet of the rhea (Martella et al, 1996). All forces were calculated assuming static equilibrium.…”

Section: Kinesis In Palaeognathous Birdssupporting

confidence: 51%

Cranial kinesis in palaeognathous birds

Gussekloo

Bout

2005

Journal of Experimental Biology

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Muscle forces are more than sufficient to overcome bending forces and to elevate the upper bill. The resistance against bending by the bony elements alone is very low, which might indicate that bending of bony elements can occur during food handling when muscles are not used to stabilise the upper bill. Model calculations suggest that the large processi basipterygoidei play a role in stabilizing the skull elements, when birds have to resist external opening forces on the upper bill as might occur during tearing leafs from plants. We conclude that the specific morphology of the palaeognathous upper bill and PPC are not designed for active cranial kinesis, but are adapted to resist external forces that might cause unwanted elevation of the upper bill during feeding.

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Section: Kinesis In Palaeognathous Birdssupporting

confidence: 51%

Cranial kinesis in palaeognathous birds

Gussekloo

Bout

2005

Journal of Experimental Biology

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“…), can be described as browsing, which means eating a wide variety of plant material with some occasional carnivorous food. The food preferences of the greater rhea in the wild (Martella et al, 1996) suggest that no fundamentally different feeding behaviours are required, other than the ones analysed in our study. The diet consists of a wide variety of food items, but is mainly vegetarian (Mosa, 1993;Martella et al, 1996;Quin, 1996).…”

Section: Kinematic Analysismentioning

confidence: 70%

“…This species has a general palaeognathous PPC configuration (McDowell, 1948) and its natural history and behaviour are well known (Raikow, 1968(Raikow, , 1969Bruning, 1974;Martella et al, 1995Martella et al, , 1996Reboreda and Fernandez, 1997). For the analysis two animals, one male and one female, were trained to feed on several food types within the experimental set-up.…”

Section: Methodsmentioning

confidence: 99%

The kinematics of feeding and drinking in palaeognathous birds in relation to cranial morphology

Gussekloo

Bout

2005

Journal of Experimental Biology

101

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Cranial kinesis is an important feature in avian feeding behaviour and involves the transmission of quadrate movement to the upper bill by the Pterygoid-Palatinum Complex (PPC). The PPC in Palaeognathae is remarkably different from that found in Neognathae. In this study we analyse whether the special morphology of the PPC is an adaptation to the feeding behaviour of the Palaeognathae. Behavioural analyses of the rhea Rhea americana showed that the feeding behaviour of the rhea is typical 'Catch and Throw' behaviour, independent of the size of the food item. Drinking is achieved by a scooping movement followed by a low-amplitude tip-up phase. During feeding rhynchokinetic movements of the upper bill were observed. However, cranial kinesis was limited and may differ from rhynchokinesis in neognathes as a clear bending zone seemed absent. Since the movement patterns are considered very similar to the basic feeding behaviour in neognathous birds it is concluded that the specific morphology of the PPC is not the result of specific functional demands from palaeognathous feeding behaviour.

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“…Rheas are reported to be herbivores, with only low insect ingestion by adults (Martella et al 1996, Pereira et al 2003, Comparatore and Yagueddú 2007, Paoletti and Puig 2007, Puig et al 2013) but more in juveniles (Schetini de Azevedo et al 1996). Compared to Ostriches and Emus, Rheas appear to be intermediate in the present study, both in terms of digesta retention times and the derived gut fill (Figure 3).…”

Section: Discussionmentioning

confidence: 99%

Comparative digesta retention patterns in ratites

Frei

Ortmann

Reutlinger³

et al. 2015

The Auk

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Ratites differ distinctively in the anatomy of their digestive tract. For example, Ostriches (Struthio camelus) have a particularly long, voluminous colon and long paired caeca, Rheas (Rhea spp.) are characterised by a short colon with particularly prominent paired caeca, and Emus (Dromaius novaehollandiae) -have neither very prominent caeca nor a prominent colon. We tested whether digesta excretion patterns corresponded to these differences in anatomy, expecting Ostriches to have the longest and Emus the shortest digesta retention times, and Rheas possibly showing a selective retention of fluids observed in other birds and mammals with prominent caeca. We used 6 Ostriches (97-123kg), 5 Greater Rheas (R. americana, 22-27kg) and 2 Emus (32-34kg) fed a common diet of alfalfa pellets ad libitum in captivity. Intake per unit of metabolic body mass did not differ between Ostriches and Rheas but was significantly higher in Emus, which also displayed higher defecation frequencies and lower fiber digestibility. Mean digesta retention time for small fiber particles (2 mm) differed significantly among species ; Emu: 1.3-1.8h), but there were no differences between the retention of 2 mm or 8 mm particles or a solute marker within species. The shape of the marker excretion curves corresponded to digesta mixing in the digestive tract of Ostriches and Rheas but not Emus. The calculated dry matter gut fill (% of body mass) was significantly higher in Ostriches (1.6-1.8) than Rheas (0.3-1.0) and Emus (0.2). Ostriches had the highest, and Emus the lowest fecal dry matter concentration. These physiological findings match the differences in digestive anatomy and support the concept that in ratites, herbivory -and hence flightlessness -evolved repeatedly in different ways. ABSTRACT Ratites differ distinctively in the anatomy of their digestive tracts. For example, Common Ostriches (Struthio camelus, hereafter Ostriches) have a particularly long, voluminous colon and long, paired caeca; Rheas (Rhea spp.) are characterized by a short colon with particularly prominent paired caeca; and Emus (Dromaius novaehollandiae) have neither prominent caeca nor a prominent colon. We tested whether digesta excretion patterns corresponded to these differences in anatomy, expecting Ostriches to have the longest and Emus the shortest digesta retention times, and Rheas possibly showing a selective retention of fluids observed in other birds and mammals with prominent caeca. We used 6 Ostriches (97-123 kg), 5 Greater Rheas (R. americana, 22-27 kg), and 2 Emus (32-34 kg) fed a common diet of alfalfa pellets ad libitum in captivity. Intake per unit of metabolic body mass did not differ between Ostriches and Greater Rheas but was significantly higher in Emus, which also displayed higher defecation frequencies and lower fiber digestibility. Mean digesta retention time for small fiber particles (2 mm) differed significantly among species (Ostrich: 30-36 h; Greater Rhea: 7-19 h; Emu: 1.3-1.8 h), but there were no differences between the retention o...

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Diet of Greater Rheas in an Agroecosystem of Central Argentina

Cited by 50 publications

References 0 publications

Cranial kinesis in palaeognathous birds

Cranial kinesis in palaeognathous birds

The kinematics of feeding and drinking in palaeognathous birds in relation to cranial morphology

Comparative digesta retention patterns in ratites

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