Having the Sand River flow through the heart of Londolozi is our biggest contributor to the diversity of wildlife we see here. This pristine body of water is the home to many different animals, ranging from catfish to hippos. One reptile in particular thrives in these waters, the Nile Crocodile.
As we enter into our winter months, the dry season at Londolozi, crocodiles around Londolozi will start gearing up for their mating season. The male crocodiles will begin their courtship behaviour and look to establish dominance over each other. What follows once dominance is established is something quite remarkable.
Breeding strategy:
Crocodiles are renowned for their breeding rituals, which unfold with remarkable precision year after year. When the Sand River recedes, revealing the sandy shores it presents a perfect time to begin nesting. But before the females fall pregnant, the males will go through a process of gaining dominance over each other, where they bellow, blow bubbles and fight to get the upper hand on their rivals.
A crocodiles vertical pupils narrow or broaden depending on the availability of light, one of the features that enables them to live the mostly nocturnal lives that they do
Mating will commence in the water and once impregnated females will search for a suitable sight to lay their eggs. Females meticulously construct nests by digging holes in the sand, where they deposit their clutch of eggs, often depositing around 50 eggs or so. These excavated nests serve as incubators for the eggs, safeguarding the precious cargo from predators and other environmental threats.
A mating pair, the whole process will take 10 or so minutes.
Temperature-dependent Sex Determination:
For me, one of the most remarkable aspects of Nile Crocodile reproduction is the temperature-dependent sex determination exhibited by their eggs. Unlike mammals, whose offspring’s sex is determined by genetic factors, the sex of crocodiles is influenced by the temperature of the nesting environment. Once the female has found an adequate spot to dig and lay her eggs, the female guards the nest site vigilantly, protecting it from potential threats such as predators and disturbances.
The incubation period for Nile Crocodile eggs is relatively long, typically lasting around 80 to 90 days. During this time, the female may occasionally excavate the nest to check on the eggs and adjust their position to ensure proper incubation conditions. Warmer temperatures often between 31-34 degrees Celsius tend to produce male hatchlings, while cooler temperatures around 26-30 degrees Celsius result in females. This phenomenon is known as temperature-dependent sex determination. Underscores the critical role of environmental factors in shaping the reproductive outcomes of these ancient reptiles.
A small Crocodile we found late one evening.
From their impressive courtship displays that I have only had the privilege of seeing a few times, to an extremely unique and wonderful sex determination of their eggs, there is a lot more than meets the eye when viewing these large reptiles. We are just at the beginning of the courtship stages so we will definitely be on the lookout for bubbles being blown and listening out for bellowing while in and around the Sand River!
Patrick, Wow! Never knew this about the temperature. So would Sept/Oct be the best time to potentially see baby crocs?
Thank you Patrick for your interesting story on the Nile crocodiles Temperature Dependant Sex Determination. So unique in their own way these reptiles. Warmer temperatures will bring about the males and cooler temperatures the females. I am petrified of them and know that they can be brutual. Keep us up to date with the courtship please.
Thanks for the information Patrick. The nile crocodile is certainly a reptile to respect.
First of all, the photos accompanying your blog are fantastic as oftentimes we can only see a small fraction of their body, when submerged, during a drive. Secondly, interesting fact that temperature determines the sex and in fact all the offspring will be the same sex. Always great to learn new information about nature’s creatures.
Temperature-dependent sex determination is a phenomenon I’ve never heard of – amazing! Thanks for the biology lesson, Patrick!
Very cool Patrick! Please keep us updated as the season progresses!!
I would love to see video of the bellowing and courtship behaviors. Maybe Sean will be able to capture some for the video safari. Our resident painted turtles have been nesting in our neighborhood, and I believe their sex is also temperature dependent. It begs the question of how these species will survive given rising global temperatures. Since they have existed relatively unchanged for millennia, I’m guessing they’ll be just fine. But too many males could theoretically throw things off. I suppose the nests are such that the temperature differs depending on the various depths of the eggs? Perhaps that will be the saving grace.
A fascinating overview, Patrick. I thrive on these sort of tidbits that aren’t normally part of the routine safari (as if there’s such a thing!).
Crocodiles are certainly fascinating animals. Thanks for this interesting blog on them, Patrick.