Body size development of captive and free-ranging African spurred tortoises (Geochelone sulcata): High plasticity in reptilian growth rates

Ritz, Julia; Griebeler, Eva Maria; Huber, Ruth; Clauß, Marcus

doi:10.5167/uzh-36147

Cited by 4 publications

(4 citation statements)

References 15 publications

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“…In the present study, we examined relative quantity discrimination using food pieces in African spurred tortoises ( Centrochelys sulcata ); this species is herbivorous and widely distributed across sub-Saharan Africa (Ritz et al 2010 ). Whilst little research has been done on the visual perception of this species, research with other tortoise species has revealed relatively well-developed visual acuity (Wilkinson et al 2013 ) and color perception (reviewed by Wilkinson and Glass 2018 ).…”

Section: Introductionmentioning

confidence: 99%

Slowly walking down to the more food: relative quantity discrimination in African spurred tortoises (Centrochelys sulcata)

2023

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Quantity discrimination, is thought to be highly adaptive as it allows an organism to select greater amounts of food or larger social groups. In contrast to mammals, the processes underlying this ability are not as well understood in reptiles. This study examined the effects of ratio and number size on relative quantity discrimination in African spurred tortoises (Centrochelys sulcata). To assess these effects, tortoises were presented with trays containing favored food pieces in all possible number combinations between 1 and 7. The tortoises had to approach the tray they perceived as having the larger quantity. If correct, they received one piece of food as reinforcement. The results revealed that relative quantity discrimination was influenced by the ratio between the numbers of pieces, with performance improving as the ratio between the numbers increased. This finding suggests that the approximate number system or analogue magnitude estimation may control their behavior. However, as the number size increased, their performance declined, also suggesting that the approximate number system alone could not explain the present results.

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Section: Introductionmentioning

confidence: 99%

Slowly walking down to the more food: relative quantity discrimination in African spurred tortoises (Centrochelys sulcata)

2023

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“…The high CF content of diets for captive reptiles is important for reducing the feed intake and thus the growth rate (28, 30, 31, 32). Captive reptiles grow much faster than free-ranging ones (2,3,15,25,33,34). In the diet of Galapagos giant tortoises (Geochelone nigra), CF may reach 30-40% on DM basis which might be the case in other herbivorous chelonians as well (29).…”

Section: Discussionmentioning

confidence: 99%

“…Chelonians are commonly kept pets. Overweight, accelerated growth rate and metabolic bone disease of nutritional origin are common as a result of inadequate nutrition and housing (1,2,3,4,5). The natural diet of aquatic chelonians consists of several animal species, and seasonality is strong in the case of tortoises (6,7,8,9,10,11,12,13).…”

Section: Introductionmentioning

confidence: 99%

“…The natural diet of aquatic chelonians consists of several animal species, and seasonality is strong in the case of tortoises (6,7,8,9,10,11,12,13). Captive chelonians should be fed a natural diet to achieve a growth rate similar to that of free-ranging animals (2,3,7,15). The energy expenditure of reptiles is only 25-35% that of mammals (16).…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Commercial Tortoise and Turtle Feeds

Hetényi

Andrásofszky²

2022

SVR

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Captive chelonians should be fed a natural diet to achieve a growth rate similar to that of free-ranging animals. A wide range of commercially formulated foods dedicated to chelonians is available. Feeding commercial foods has the advantage of convenience. On the other hand, species-specific information on the nutritional requirements of chelonians is not available yet. The aim of this study was to analyse and evaluate commercial pellets and feeds for chelonians. Commercial pellets (ntortoise = 7, nturtle = 7, from 6 companies) dedicated to carnivorous aquatic turtles and herbivorous terrestrial tortoises, and other aquatic turtle feeds (lyophilised beef heart, dried aquatic invertebrates, and whole frozen fish) were bought in pet shops. Whole frozen fish served as a reference feed for carnivorous aquatic turtles. The chemical composition as well as calcium (Ca) and phosphorus (P) contents were determined. Single-sample t-test was used with the label information as null hypothesis and the results of own parallel analyses for crude protein (CP), ether extract (EE), crude fibre (CF), Ca and P. The labelling of some of the pellets was deficient as nutritive values, Ca or P data were missing (tortoise pellets: 4 out of 7; turtle pellets: 5 out of 7). The label data differed significantly (p<0.05) from the results of our own analysis for 13 out of the 14 pellets. None of the tortoise pellets met the requirements of the animals completely. Because of the inadequate Ca:P ratio only one turtle pellet could be accepted. Accordingly, none of the commercial pellets can be recommended as main or only feed. Key words: nutrition; pellet; metabolic bone disease; chelonian VREDNOTENJE KOMERCIALNIH ŽELV IN KRME ZA ŽELVE Izvleček: Želve v ujetništvu je potrebno hraniti z naravno krmo, da dosežejo podobno stopnjo rasti kot živali v prosti reji. Na voljo je širok izbor komercialno pripravljene hrane za želve. Prednost hranjenja želv s komercialno hrano je priročnost, vendar podatki o prehranskih potrebah za posamezne vrste želv še niso na voljo. Namen te raziskave je bil analizirati in ovrednotiti komercialne pelete in krmo za želve. V trgovinah za živali smo od 6 podjetij kupili komercialne pelete (npeleti za vodne želve = 7, npeleti za kopenkse želve = 7) za mesojede vodne in rastlinojede kopenske želve ter drugo krmo za vodne želve (liofilizirano goveje srce, posušene vodne nevretenčarje in zamrznjene cele ribe). Zamrznjene cele ribe smo uporabili kot referenčno krmo za mesojede vodne želve. Določili smo kemično sestavo in vsebnost kalcija (Ca) ter fosforja (P). Za ničelno hipotezo smo uporabili T-test enega vzorca s podatki na etiketi in rezultate lastne paralelne analize za surove beljakovine (an gl. crude proteins, CP), ekstrakt etra (angl. ether extract, EE), surovo vlaknino (angl. crude fibre, CF), Ca in P. Oznake nekaterih peletov so bile pomanjkljive, saj so manjkali podatki o hranilnih vrednostih, Ca in P (npeleti za kopenske želve = 4 od 7, npeleti za vodne želve = 5 od 7). Podatki na etiketi so se bistveno razlikovali (p < 0,05) od rezultatov naše analize pri 13 od 14 vrst peletov. Nobeni peleti za kopenske želve niso v celoti izpolnjevali potreb živali. Zaradi neustreznega razmerja Ca : P smo kot ustrezno določili le eno izmed 7 vrst peletov za vodne želve, zaradi česar nobenih od komercialnih peletov nismo določili kot priporočljivih za glavno ali edino krmo za želve. Ključne besede: prehrana; peleti; presnovna bolezen kosti; želve

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Slowly walking down to the more food: Relative “number” discrimination in African spurred tortoises (Centrochelys sulcata)

Tomonaga

Haraguchi

Wilkinson

2023

Preprint

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Numerical discrimination is thought to be highly adaptive as it allows an organism to select greater amounts of food or larger social groups. The processes underlying this ability are well understood in mammals with two systems being posited to control behavior, the approximate number system, which uses the ratios between numbers and the object file system which tracks individual small numbers. Much less in known in reptiles, the work that is available suggests that chelonia may use the ratios between the numbers to discriminate numerical values. This experiment examined the effect of ratio and number size on relative numerical discrimination in African spurred tortoises (Centrochelys XXXulcate). To assess this, tortoises were presented with trays containing favored food in all possible number combinations between 1 and 7. The tortoise had to approach the tray it perceived as having the larger number, if correct, the tortoise received one piece of reinforcement. Each tortoise received 36 pairings of each stimulus combination. The results revealed that numerical discrimination was influenced by the ratio between the numbers, with performance improving as the ratio between the numbers increased. This suggests that the approximate number system may be controlling their behavior. However, the opposite tendency was observed for the larger numbers, suggesting that an object-file system may also be involved in numerical discrimination.

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Body size development of captive and free-ranging African spurred tortoises (Geochelone sulcata): High plasticity in reptilian growth rates

Cited by 4 publications

References 15 publications

Slowly walking down to the more food: relative quantity discrimination in African spurred tortoises (Centrochelys sulcata)

Slowly walking down to the more food: relative quantity discrimination in African spurred tortoises (Centrochelys sulcata)

Evaluation of Commercial Tortoise and Turtle Feeds

Slowly walking down to the more food: Relative “number” discrimination in African spurred tortoises (Centrochelys sulcata)

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