Mating in the tawny nurse shark is known to occur from July to August off Madagascar . Adult females have one functional ovary and two functional uteruses . The mode of reproduction is aplacental viviparity , meaning that the embryos hatch inside the uterus ; females in captivity have been documented depositing up to 52 non @-@ viable egg capsules , which have led to erroneous reports of this shark being oviparous . The egg capsules of this species are onion @-@ shaped , with thin , brown , translucent shells . The tawny nurse shark is the only carpet shark in which there is oophagy : once the developing embryos exhaust their supply of yolk , they gorge on eggs produced by the mother and acquire the distended abdomen characteristic of such oophagous embryos . Unlike in mackerel sharks , the eggs consumed by the embryos are large and shelled rather than small and undeveloped . There is no evidence of sibling cannibalism as in the sand tiger shark ( Carcharias taurus ) .