A study published in 2008 analysed the connection between reproduction of Argentine boas (Boa c. occidentalis) and devastation of their habitats. The conclusion is overwhelming...
The Argentine Gran Chaco has been an endurer of South American deforestation for a long time. According to this article, 2,2% of forests disappears each year for good, 85% of subtropical forest have disappeared in the last 30 years. Although secondary vegetation may evolve in those deforested areas, changed geographical condition certainly have effects on species' behaviour (etology), including reproduction behaviour of Argentine boas.
Argentine boas are typically native to dry forest, however they can also occur in tropical forest, as well. Certain sources claim that woodlands have in important role in controlling the temperature in gravid females, because boas may adjust their body temperature by selecting trees of certain heights. Authors also mention that boas are loath to reproduce in extirpated forestal regions repleaced by scrublands.
Informations were collected through seven years, from 1996 to 2003 for this study, meanwhile 173 specimens (91 males, 82 females) were examined. Reproduction activity, size of reproductive organs, cycles, size of litters were estimated by using ultrasoundography.
Interestingly, in the breeding season sexually active males and non-active females took an average of 1,5 km distance, while sexually-active females averaged only 0,09 km.
By the years passing by, average weight of gravid females permanently decreased, that suggests smaller gravid females with less neonates being born each year. Weigth of males and volume of their testis have also decreased which may refer to lower sexual activity in their changed habitat. That is also confirmed by the fact that 33% of males from primary forestal areas had bigger sexual organs, in contrast with males from secundary scrub areas.
We conclude that boas survived the extirpation of primary forests have lower sexual activity in both sexes, gravid females are smaller, producing less neonates. Males- having lower acitvity -probably mate to less females with less successful ratio. These phenomenons alltogether are leading to a rapid shrinkage of population and possibly to extintion of Argentine boas (Boa c. occidentalis). Authors recommend strict and pressing protection of habitat. I suggest to do the same.
Source: Gabriela Cardozo - Margarita Chiaraviglio: Landscape changes influence the reproductive behaviour of a key ‘capital breeder’ snake (Boa constrictor occidentalis) in the Gran Chaco region, Argentina
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