Nile Crocodile

[Vodmeister]

Local names
Mamba, Garwe, Ngwenya

 Conservation Status
 Lower Risk, least concerned (LR/lc)
Currently there are an estimated 250,000 to 500,000 Nile crocodiles alive in the wild; 4,000 in the Kruger National Park, about 800 in the Greater St. Lucia Wetland Park and 2,000-3,000 in the Ndumu Wildlife Conservation Area.

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Sauropsida
Order: Reptilia
Family: Crocodylidae
Subfamily: Crocodylinae
Genus: Crocodylus
Species: C.niloticus

Crocodilians are archosaurs, early forms splitting off from the other reptiles during the Triassic about 200 million years BP. Like birds, crocodilians have gizzards and a 4-chambered heart, not the 3-chambered heart of other reptiles. Crocodilians consist of three families and 23 species
Successful, sustainable programs focusing on ranching crocodiles for their skins have been successfully implemented throughout Africa. In 1993 80,000 Nile crocodile skins were commercially produced, the majority from ranches in Zimbabwe and South Africa. In central and west Africa, which makes up about two-thirds of the Nile crocodile's habitat, the situation is grimmer. The population in this area is much more sparse and is in competition with the sympatric African slender-snouted crocodile and the African dwarf crocodile.

Description
All crocodilians have short walking legs, a powerful tail and incredibly powerful jaws with 64-68 razor-sharp, conical teeth. The teeth are replaced about 45 times during a life span. The tongue is not split as in most reptiles and contains excretion glands for the disposal of excess salt from the body that allows the crocodile to inhabit both fresh and saline water.
Crocodilians have a palatal valve on the back of the tongue that closes against the upper jaw, sealing the throat while underwater. Eyesight is excellent both during day and at night. The eyes lie laterally on top of the head and protrude above the water when the animal surfaces. They posses clear nictitating membranes or third eyelids that protect the eye when swimming or hunting and increases underwater vision. Crocodiles also possess ossified scales on the back and tail called osteoderms that form a protective armour. With the webbed hind feet and tail they can swim at 30-35 km/hr. They can walk on land and gallop for short distances at speeds ranging up to 14 km/hr.
Nile crocodiles are known to reach a greater size in the hot Afro-tropics; individuals >5 m and >750 kg are sporadically reported from Lake Nasser in Egypt. They are smaller in cooler sub-tropical regions such as southern Africa, average length for adult males 4.2 m. The largest living specimen, a notorious man-eater from Burundi, was believed to be between 6.2-7.5 m.
The largest known Nile crocodile from South Africa was captured alive by J.G. Kulmann in the Mutale River near Lake Funduzi in Venda. It had a total body length of 5.499 m (18 feet 1/2”) and a mass of 905.7 kg. In Africa, a specimen collected in the Simliki River in Uganda in 1953 measured 5.94 m (19 feet 57/8”) and weighed 600 kg and another in the Okavango swamps in Botswana in 1968 measured 5.87 m (19 feet 31/8”) with a mass of 600 kg.


Characteristic Morphometrics of both sexes
Adult body weight(kg)
400-500 (max. 900)[M] 150-300 (max. 600) [F]

Hatchling body weight(g)
100-110 [both sexes]

Adult body length (m)
4.0-5.5 (max. 6.1)[M] 3.0-4.0 (max. 5.0)[F]

Hatchling body length(cm)
25-30[both sexes]

Age of maturity(years)
10-12 (at 3 m body length) [M}& 10-12 (at 2-2.25 m body length) [F]

Distribution & Habitat requirement
The crocodile is largely restricted to living in tropical and sub-tropical environments such as the Afro-tropics of Central Africa. They prefer warmer water of 22-30°C. They live in lakes, rivers, freshwater swamps and brackish water, in deep pools and on sand banks with suitable nesting spots and a sufficient food supply. Surface water is essential. If it evaporates a crocodile will either migrate in search of another source or will aestivate. Fast flowing water and streams are generally avoided. Slightly murky water is preferred over clear water.


Behavior
Crocodiles are cold-blooded and do not have constant body temperature. The core body temperature is built up to a maximum of 38°C by basking in the sun during daylight hours. The energy generated is used for digesting food, hunting and social behaviour. Without sufficient core temperature, a crocodile cannot digest food and in an extended period of cold may become poisoned by the undigested, rotten food matter in its stomach. After sunset the core body temperature drops rapidly to a minimum of 15°C. During drought periods, a crocodile may enter a hibernation which can last for several months. They dig a den in a dry riverbed or riverbank and retreat into it and can survive without feeding for up to two years. They also migrate several kilometres across dry land in search of alternative resources.

Feeding & Nutrition
The diet of this mono-gastric, carnivorous predator changes markedly with age. Juveniles feed on insects, spiders, snails, gastropods and mussels. Young crocodiles feed mostly on toads, frogs and small fish such as Clarias, Labeo and Tilapia spp., while sub-adults feed increasingly on reptiles such as terrapins, pythons, snakes, water-birds, crabs, and rodents. With age the diet changes to barbel (catfish) and larger mammals up to the size of young giraffe, buffalo and elephant. On average barbel comprises 70% of the diet of adults. They are known to prey on plains zebra, Cape buffalo, warthog, hyaena, baboon, blue wildebeest, impala, giraffe, big cats (especially lion) and other crocodiles. When taking prey on the waters edge an adult crocodile raises the fore quarters of its body to a height of 1.2 m above the water surface and simultaneously throws its entire body forward in a charge of 10-20 m onto dry land.

Weekly food consumption (adults)

• ~5-8kg [M]
• ~4-5kg [F]

Crocodiles have an ectothermic metabolism which allows them to survive lengthy periods between meals, although when they do eat they can consume up to half their body mass at one time. During summer a 4 m adult will consume a large meal once in 2-3 weeks. Sub-adults of 1.5 m eat once a week while juveniles feed daily. Fresh food is preferred but sometimes large, thick-skinned prey is allowed to rot under overhanging banks or among submerged tree roots until it can be dismembered. As crocodiles cannot chew, large chunks are swallowed whole. If the prey is too large, smaller portions are torn off by jerking the head to and fro, or by twisting or spinning on the crocodile’s own axis, the so called “death roll”.



Groups of Nile crocodiles sharing a kill use each other for leverage in order to perform death rolls. The head must be lifted above surface in order to consume prey as crocodiles cannot swallow underwater. Carrion is taken only when fresh food is not available. The powerful enzymatic digestive juices of crocodiles completely digest bones, hooves and feathers but being poikilothermic animals, digestion is promoted by higher temperatures. In warm water of >22-30°C crocodiles remain submerged for approximately 15 min, but in cool water of 14-20°C up to 60 min and in cold water of<12°C for up to two hours.

Social structure & reproductive characteristics
Crocodiles are gregarious animals. Groups are known as “floats” when in the water or “basks” when on land. Group size depends on food abundance and may range from two to >100 individuals. When food resources are depleted or when the surface water dries up, groups tend to break up and individuals may become temporarily solitary. Individuals in groups continuously communicate with a variety of pitched vocals. Body contact is tolerated and they often lie against or over each other.

In the wild, both sexes reach sexual maturity at an age of 10-12 years. The onset in males occurs at a length of about 2.8-3 m with an approximate mass of 200 kg and in females at a length of 2-2.5 and a mass of 150 kg. Females start mating on reaching sexual maturity. However, males only begin mating at an age of 15 years when they are 3.5-4 m long and have a mass of 400 kg. Crocodiles are divided into hole-nesters and mound-nesters, with the Nile crocodile being a hole-nester. The preferred nesting locations are sandy shores, dry stream beds and riverbanks. The female digs a hole 40-50 cm deep a few meters from the bank and lays 25-90 eggs. The mother covers the eggs with a layer of sand and guards them for the three month incubation period. The mother protects her offspring for about 10 days. Mothers may form a crèche if there are multiple nests in the area. After two years the juveniles are close to 1.2 m long and leave the nest area, avoiding the territories of older and larger crocodiles. Only 2% of the hatchlings survive to live beyond a size of 1.5 m length but after this time the mortality rate drops radically as the adult crocodile has few enemies besides humans.



Clutch characteristics

• Number of eggs per clutch number: 25-90 (avg. 45)
  
• Incubation period: 90 days 
• Hatchling season: Dec-Mar
  
• Egg-laying season: Sep-Dec
  
• Hatchling dispersal age: months 3
  
• Independent at ~2 years of age( or at 1.2m TBL)
  
• Gender ratio: 1:1.5
  
• Annual population growth: ~2%
• Mating season: May-Aug
  

Bibliography

• Alderton, D. 1991. Crocodiles and Alligators of the World. Facts on File, New York.
• Blake, DK, 2006. The Nile crocodile In: Intensive wildlife production in southern Africa, Eds. J du P Bothma and N van Rooyen, Van Schaik Publishers, Pretoria.Crocodile Specialist Group, 1996. Crocodiles. IUCN, Gland, Zwitzerland.
• Grnard, S. 1991. Handbook of Alligators and Crocodiles. Florida: Kreger Publishing Company.
  
• Leslie, AJ, 1997. The ecology and physiology of the Nile crocodile in Lake St Lucia, KwaZulu-Natal, S.A. Ph.D thesis Philadelphia, Drexel University.
  
• Levy, C. 1991. Crocodiles and Alligators. London: Quintet Publishing Limited.
  
• Pooley, AC, 1982. The status of African crocodiles in 1980. In: Crocodiles. Proceedings of the 5th Working Meeting of the IUCN/SSC Crocodile Specialist Group, Gainesville, Florida. IUCN, Gland, Switzerland. pp. 174-228
  
• Steel, R, 1989. Crocodiles. London, Christopher Helm.
  
• Thorbjarnarson, J. 1992. Crocodiles-An Action Plan for Their Conservation. IUNC, Gland, Switzerland.
  
• Webb, JW, Grahame, MS. Whitehead and Peter. J, 1987. Wildlife Management: Crocodiles and Alligators. Surrey Beatty and Sons Pty Limited, Australia.
  
• Wikipedia, 2008. Crocodillians, en.wikipedia.org/wiki/Nile_crocodile
  
• www.wildliferanching.com/content/nile-crocodile-crocodylus-niloticus

[Vodmeister]

The Giant Crocodile of Burundi - Gustave


www.youtube.com/watch?v=kBkPi-35QcQ

[Supercommunist]

nypost.com/2014/04/06/officials-capture-one-ton-crocodile-that-ate-4-men/

[Ceratodromeus]

Neat accounts of Nile crocodile predation on large animals

Reference: Pienar UP (1969) Predator-prey relationships among the larger mammals of the Kruger National Park. Koedoe 12:108–176

[Ceratodromeus]

Size does matter: crocodile mothers react more to the voice of smaller offspring
Abstract

Parental care is widespread in Archosaurs (birds, crocodilians, dinosaurs and pterosaurs), and this group provides a useful model for the evolution of parent-offspring interactions. While offspring signalling has been well-studied in birds, the modulation of parental care in crocodilians remains an open question. Here we show that acoustic communication has a key role in the dynamics of crocodilian’ mother-offspring relationships. We found embedded information about the emitter’s size in juvenile calls of several species, and experimentally demonstrated that Nile crocodile mothers breeding in the wild are less receptive to the calls of larger juveniles. Using synthetized sounds, we further showed that female’ reaction depends on call pitch, an important cue bearing size information. Changes in acoustic interactions may thus go with the break of maternal care as well as dispersal of juvenile crocodilians. This process could have characterized other archosaurs displaying rapid early growth such as dinosaurs and pterosaurs.




Figure 2: Correlations between individual size (total body length) and (a) the calls’ mean pitch, and (b) the calls’ centroid of the frequency spectrum.
link to paper

[Ceratodromeus]

Nile crocodile(s) try to take down adult rhinoceros

[Ceratodromeus]

Feb 2, 2016 8:51:49 GMT 5 Ceratodromeus said:

Nile crocodile(s) try to take down adult rhinoceros

Came across the preliminary report of this event, along with other photos of the event and the sex of the rhino







From "African nature notes and reminiscences"

by Selous, Frederick Courteney(1908)



it is doubtful the crocodile wrapped its tail around anything, but instead found other was to keep itself from being dragged around by the rhino.

[Ceratodromeus]

some information on large herbivores most commonly taken by the nile crocodile, as well as a mention of a lioness apparently loosing her tail to a crocodile in a confrontation









from Crocodiles: their natural history, folklore and conservation(Guggisberg 1972)
what i find interesting is the apparent second attack on a rhino by a nile crocodile -- different from the one i've posted elsewere.

[Ceratodromeus]

MOLECULAR ANALYSES CONFIRMING THE INTRODUCTION OF NILE CROCODILES, CROCODYLUS NILOTICUS LAURENTI 1768 (CROCODYLIDAE), IN SOUTHERN FLORIDA, WITH AN ASSESSMENT OF POTENTIAL FOR ESTABLISHMENT, SPREAD, AND IMPACTS

Abstract
—The state of Florida, USA, has more introduced herpetofauna than any other governmental region on Earth.
Four species of nonnative crocodilians have been introduced to Florida (all since 1960), one of which is established.
Between 2000–2014 we field-collected three nonnative crocodilians in Miami-Dade County, Florida, and one in Hendry
County, Florida. We used DNA barcoding and molecular phylogenetics to determine species identification and native
range origin. Also, we described diet, movement, and growth for one crocodile. Our molecular analyses illustrated that
two of the crocodiles we collected are most closely related to Nile Crocodiles (Crocodylus niloticus) from South Africa,
suggesting this region as a source population. We, thus, documented the first known introduction of C. niloticus in
Florida. Two, and possibly three of the introduced crocodiles shared the same haplotype, suggesting they are likely from
the same introduction pathway or source. One animal was captured, measured, marked, and released, then recaptured 2
y later allowing us to calculate growth rate (40.5 cm/y) and movement. The most likely route of travel by waterway (i.e.,
canal) illustrates that this animal traveled at least 29 km from its original capture site. One crocodile escaped from a
facility in Hendry County, Florida, and survived in 1,012 ha of semi-wild habitat for three to four years, confirming that
this species can survive in southern Florida.

"The first crocodile
(approximately 1.2–1.5 m TL; photographic voucher
UF-Herpetology 175632) in this study escaped from its
enclosure in 1996 or 1997 at Billie Swamp Safari,
Seminole Reservation, Hendry County (26.330348°N,
81.055936°W; datum WGS84; Jonathan Vasquez, pers.
comm.). This crocodile was somewhat contained by a
perimeter fence within the 1,012 ha property. In 2000, it
was finally recaptured by Billie Swamp Safari staff and
measured 3 m TL. We were unable to secure a tissue
sample from this crocodile.
The second crocodile (UF-Herpetology 175743), a
hatchling, was captured by Robert Freer on 14 April
2009 on the house porch of a resident at 24800 SW 193
Avenue, Miami, Miami-Dade County (25.534833°N,
80.504653°W), and subsequently transported to
Kliebert’s Turtle and Alligator Farm in Hammond,
Louisiana. In June 2015 we acquired a tissue sample
from this crocodile. The third crocodile (UFHerpetology
165995) was a female captured on 27
October 2011 at the Preston B. Bird/Mary Heinlein Fruit
and Spice Park, Homestead, Miami-Dade County
(25.53385°N 80.49348°W; datum WGS84; Fig. 1), and
subsequently kept in captivity by JAW. It measured
57.7 cm SVL, 115.2 cm TL, 15.3 cm HL, and weighed
4.4 kg.

The fourth crocodile (UF-Herpetology 173082) was a
female (86.3 cm TL) captured on 13 March 2012 in a
canal in Homestead, Miami-Dade County (25.50632°N,
80.47343°W). This crocodile was released and
recaptured 9 March 2014 in Everglades National Park
(ENP; 25.61707°N, 80.5753°W; U.S. National Park
Service, unpubl. report), and measured 23.6 cm HL, 88.0
cm SVL, 167.9 cm TL, 43.6 cm TG, and weighed 17.0
kg. Its stomach contained remains of a Largemouth
Bass (Micropterus salmoides). Straight-line distance
over land between primary and secondary capture sites
was 16 km; however, the most likely route of travel by
canal was 29 km."


link to study

[Ceratodromeus]

On terrestrial hunting by crocodilians
"Crocodilians are generally considered to
be specialised predators hunting in the water
or at the water edge (Neil, 1971). Their terrestrial
activities such as nesting, migrating, aestivating/
hibernating and basking are well known and
documented in most overviews of crocodilian
biology. Despite abundant anecdotal evidence
of terrestrial hunting (mostly in the form of
scary campfire stories), this aspect of crocodilian
behaviour has never been studied nor scientifically
described. Observations made during a study of
crocodilians in the wild in 2006-2010, mostly on
American alligator (Alligator mississippiensis),
Nile crocodile (Crocodylus niloticus), and to
a lesser extent on other species, suggest that
terrestrial hunting may be more common than
previously thought."

Nile crocodiles(Crocodylus niloticus)
Pooley (1982) mentioned his observation of two
Nile crocodiles carrying a recently killed Nyala
(Tragelaphus angasii) overland, but it was not
clear if the animal had been killed on land.
In September 2008 in South Luangwa National
Park (Zambia), at 02:15, I observed a 2.5 m Nile
crocodile unsuccessfully chase a juvenile Bushbuck
(Tragelaphus sylvaticus) for 5-6 m across a dry,
elevated river terrace at least 100 m from the water
edge. Interviews with local hunters, safari guides
and game rangers suggested that Nile crocodiles
are occasionally seen on roadsides during night
drives in South Luangwa and Lower Zambezi
National Parks (Zambia), Mudumu and Mamili
National Parks (Namibia), Chobe and Moremi
National Parks (Botswana), Lilongwe National
Park (Malawi), and Murchison Falls National Park
(Uganda).
I have observed terrestrial behaviour at the
Oromo River Delta, Ethiopia (n=1 in 44 hours of
nocturnal searching), Mahango Game Reserve,
Namibia (n=2 in 56 hours of nocturnal searching and
driving), and at Simangaliso Wetland Park, South
Africa (n=1 in 6 hours of nocturnal searching)
Terrestrial behaviour on these occasions was
always by crocodiles of between 2-3.5 m. In the
latter case, a 2.5 m long crocodile was observed
catching and swallowing a large toad (Bufonidae)
as it was moving along the trail. Once located,
each crocodile was observed for 20-30 min to see
if it would start moving, but no attempts to change
location were ever seen. The fact that predation
attempts were seen twice in less than 2 hours of
observing Nile crocodiles on land at night suggests
that terrestrial hunting is possibly an effective
alternative hunting strategy.
dinets.info/Pages%20from%20Bulletin%20114%20Dinets.pdf

[Ceratodromeus]

Climbing behaviour in extant crocodilians

"Extant crocodilians are generally considered to be
predominantly or semi-aquatic. And, although the
role of terrestrial activity in their natural history is
increasingly recognized (see, for example, an overview
of terrestrial hunting in crocodilians in Dinets, 2011),
they are virtually never thought of as animals capable
of climbing. Their non-arboreality is often taken for
granted in various analyses of tetrapod limb evolution
and behaviour of extinct Archosauria (see BirnJeffery
et al., 2012, for a discussion of the subject
and a bibliography). Climbing behaviour in extant
crocodilians has never been described in detail in the
scientific literature, though it was briefly mentioned by
Tarsitano & Hecht (1980), Frey (1988), and, earlier,
Guggisberg (1972) who wrote that baby crocodiles “can
climb into bushes, up trees and even hang on reeds like
chameleons."
Despite this limited documentation, the ability of
crocodilians (mostly juveniles) to climb trees is well
known to local residents in some locations. They
reported routinely observing basking in mangrove
trees by juvenile American crocodiles (Crocodylus
acutus) near Tulum (Quintana Roo, Mexico, Jason
Cleinsten pers. comm.), in mangrove trees up to 10 m
above ground by juveniles of the same species in Isla
de Salamanca National Park (Barranquila, Colombia,
Juan Cabrera pers. comm.) and by juvenile estuarine
crocodiles (C. porosus) near Sorong (West Papua,
Indonesia, Benyamin Syatfle pers. comm.). A photo
of a Nile crocodile (C. niloticus) climbing a low
tree trunk was obtained in March 2012 by Grant and
Dimari Oliver in Okavango Delta, Botswana (Larien
Spies pers. comm.). Photos of a juvenile New Guinea
crocodile (C. novaeguineae) basking on a tree trunk
growing at an angle were taken at Elevala River (Papua
New Guinea) by Michael Lech (pers. comm.). A photo
of a Philippine crocodile (C. mindorensis) in a tree
can be seen in van Weerd & van der Ploeg (2012).
Crocodiles (presumably Central African slendersnouted
crocodile Mecistops cataphractus, see notes
on taxonomy below) are reportedly often observed in
Odzala-Kokoua National Park (Republic of Congo)
as they bask in trees in very dense rainforest (Jackie
Appleton unpubl. obs.). Juvenile Siamese crocodiles
(C. siamensis) in Laos (Octávio Mateus pers. comm.)
and American alligator (Alligator mississippiensis) in
USA (Shawn Heflick pers. comm.) have been observed
on tree branches 0.5-1 m above the water. A photo of a
sub-adult American alligator perched on a tree branch
2-3 above the water (Fig. 1) was obtained at Pearl River
Delta, Mississippi (Kristine Gingras pers. comm.).
Captive dwarf crocodiles (Osteolaemus sp.) often climb
tree branches (Ralf Sommerlad pers. comm.). One adult
dwarf crocodile escaped from its enclosure at the Bristol
Zoo (UK) by climbing up a tree growing at an angle and
then over the barrier (John Dickson pers. comm.).
In most of these cases, crocodilians are observed
low above the water surface. But, as the following
observations show, they are capable of climbing higher,
sometimes into tree crowns."

Tree-climbing in the Nile crocodile
A. B. observed a Nile crocodile approx. 2 m in total
length basking on a tree in the panhandle region of the
Okavango Delta, Botswan, which
then dropped into the water as the observers passed it
in a boat. The branch was approximately 0.5 m above
the water surface. The crocodile likely climbed onto
it from the point where it dipped into the water nearer
to the bank. V. D. observed juvenile Nile crocodiles
basking on tree branches less than 1 m above the water
in Mahango Game Reserve, Namibia, in South Luangwa National Park, Zambia
, always during the
daytime.
Interestingly, all photos of Nile crocodiles basking on
tree branches that the authors could find on the Internet
also come from the southern part of the species’ range
(South Africa, Zambia, Zimbabwe and Botswana),
rather than from East Africa, where the species is
equally common and frequently observed, or from
other parts of the continent where this species, and the
West African crocodile (C. suchus), occur. In all cases,
climbing abilities seem to be less developed than in
Australian freshwater, American and Central African
slender-snouted crocodiles."
herpetologynotes.seh-herpetology.org/Volume7_PDFs/Dinets_HerpetologyNotes_volume7_pages3-7.pdf

[Ceratodromeus]

I made this post on the size of adult nile crocodiles and interactions with lions on carnivora, but it fits nicely here as well

"A large male nile crocodile would be in the ball park of 5-5.5m in total length and a mass of 600-700kg; Gerard wood, in his guiness book of animal facts & feats, wrote on an animal measuring 5.8m in total length with an estimated mass of 794-816kg, and a 4.8m animal weighing in at 680kg, all of these are of course a lot bigger than the largest lions. the figure in the OP describing the record length of a nile crocodile is an estimate, presented in Wood(1983), the slightly lower figure presented was 2300lbs. not significant but warranting clarification i guess.



The thing with crocodiles is not as tricky as it commonly portrayed to be, like a lot of large predators with wide geographic ranges they vary tremendously. ~3-4.5 is what you can expect a typical adult nile crocodile to measure in total body length. They mature around 2.5m in total body length, with this of course varying from population to population(lake rudolph males matured at either 1.8 or 3.3m in total length at extremes) as well as sex(lake rudolph females matured at 1.7 or 3.0 in total length at extremes), but these animals shouldn't really be regarded in this match up, as a young crocodile against an adult lion is very one sided. Now here is a very large (500+) sample of animals from different localities that should clear up what a typical nile will weigh, of course taking the bit i've written about sexual maturity into consideration.





As a general statement i think average adult male crocodiles are about as big as the larger lions and the adult female crocodiles are more around the size of average lions.

Now what is very interesting is that the dissertation this is from (Graham 1968), it is reported that lions do not/ had not been observed killing crocodiles over 3.2 meters in total body length, at the time this was published. That is also probably worth taking into consideration; lions don't likely kill crocodiles larger than themselves by themselves.

From Alistair Grahams 1968 dissertation on Lake Rudolph Nile Crocodiles

[Ceratodromeus]

Study on the morphometrics and biodensity of South African niles
Morphometrics, sex ratio, sexual size dimorphism, biomass,and population size of the Nile crocodile (Crocodylus niloticus)
at its southern range limit in KwaZulu-Natal, South Africa

Abstract
Animal body size and sex are requisite data for
understanding population structure and demography. Little
information exists regarding Nile crocodile, Crocodylus
niloticus, morphometrics, sex ratios of wild populations,
sexual size dimorphism and standing crop biomass. We
captured 322 C. niloticus at Lake St Lucia and Ndumo Game
Reserve, South Africa, the two largest crocodile populations
at the southern extent of the species’ range in Africa, and
measured a suite of physical characteristics to create predictive
models of body length from other morphological
attributes and body mass. Our sample included 118 hatchlings,
91 subadults and 113 adults. Strong positive allometric
relationships were found between body length metrics (total
length and snout-vent length) and other morphometrics. All
morphometric regressions were linear, with the exception of
the relationship of body length to body mass, which was
logarithmic. Among relationships of cranial morphology and
body length, we found considerable individual variation
among all size classes. The mean head width-to-head length
ratio was 1.9 ± 1.6, and mean head length-to-total length
ratio was 0.14 ± 0.005. The sex ratios for non-hatchling
individuals at both populations were essentially 1:1, but adult
sex ratios were male biased. We calculated a total standing
crop biomass of 96,867.18 kg (161.45 kg/km) and
52,640.40 kg (1504.01 kg/km) for C. niloticus at Lake St
Lucia and Ndumo Game Reserve, respectively, and an
estimated 3650 non-hatchling individuals for the province of
KwaZulu-Natal. The data presented here will help inform
crocodile management and population surveys in South
Africa, where C. niloticus is an important apex predator that
partitions aquatic resources and occasionally comes into
conflict with human beings.
[/small]
Link to study

[Ceratodromeus]

                                Surprising Discovery Shows Dozens of Mummified Baby Crocodiles
    "While preparing for a new exhibit that will allow visitors to virtually dissect a crocodile mummy, museum curators in the Netherlands were met with a surprise: What they had thought were two crocodiles wrapped up together turned out to be nearly 50.

An earlier scan, carried out in the 1990s, had already shown evidence that the nearly 10-foot-long specimen was in fact two smaller adolescent crocodiles, as opposed to one longer one. But the older scan did not clearly show any additional animals.


While preparing for a new exhibit that will allow visitors to virtually dissect a crocodile mummy, museum curators in the Netherlands were met with a surprise: What they had thought were two crocodiles wrapped up together turned out to be nearly 50.

An earlier scan, carried out in the 1990s, had already shown evidence that the nearly 10-foot-long specimen was in fact two smaller adolescent crocodiles, as opposed to one longer one. But the older scan did not clearly show any additional animals.



In this high-definition scan, the juvenile crocodiles are shown with the clear outlines of babies (in blue) around them.


CT scans offer a "really detailed" and noninvasive look at "what's going on inside" the mummies, says museum conservator Allison Lewis.

The 2,500-year-old specimen was likely a sacrifice to the crocodile god Sobek, according to Laura Weiss, a curator at the National Museum of Antiquities in Leiden, which has housed the crocodile mummy since 1828.



Ancient Egyptians believed in life after death, which could explain the sacrifice and mummification of both baby and adolescent crocodiles, Weiss added.



There is precedent for mummifying multiple crocodiles as an offering to the gods. One crocodile, probably worshipped in life as a living incarnation of Sobek (as opposed to being raised as a sacrifice), was mummified after death with 20 hatchlings and was exhibited in 2015 at the British Museum in London, and two more were studied at the Hearst Museum of Anthropology in California."
news.nationalgeographic.com/2016/11/crocodile-mummy-ancient-egypt-discovery/

[Ceratodromeus]

Nest predation and maternal care in the Nile crocodile (Crocodylus
niloticus) at Lake St Lucia, South Africa
Abstract
(Crocodylus niloticus) is largely restricted to anecdotal observations, and has not been studied quantitatively.
Consequently, we investigated their nesting biology using camera-traps over four years at Lake
St Lucia, South Africa. We obtained 4305 photographs (daylight captures = 90.1%, nocturnal = 9.9%) of
19 nest-guarding females. Of 19 monitored nests, 37% were raided by predators (mean = 12.1 ± 6.2 days
subsequent to camera placement). All females returned to their nests following first predation, and on
average returned three times between predator raids before nest abandonment.Water monitors (Varanus
niloticus) and marsh mongoose (Atilax paludinosus) were the main egg predators. Nesting raids lasted
5.9 ± 1.6 days. Diurnally females were seldom on the nest, except during cool/cloudy weather or rain,
preferring to guard from nearby shade. Females defended nests aggressively against non-human intruders.
Five Nile crocodile females were observed liberating their hatchlings from nests. A detailed sequence
of a mother excavating and transporting hatchlings revealed 13 excursions between nest and water
over 32.5 h. This, after months of continual nest attendance and defense, is illustrative of the high level
of maternal care in Nile crocodiles. Camera-trapping is an effective, non-invasive method for further
crocodile nesting behaviour research.



Fig.1 Nile crocodile nest predation (a–c) by a water monitor at the Mphathe Stream, Lake St Lucia, and (d) the female arrival at the nest after dark, subsequent to the initial raid.

Nest guarding behavior
During daylight, all Nile crocodile females guarded their nests
from the shade of nearby vegetation, although camera-traps could
not always verify the exact position of each guarding female.
However, we were able to determine that the respective daylight
guarding positions for seven females continually within camera
sensor range remained unchanged during the incubation period. On
average 14.5 ± 4.9%of photographs (n = 276) recorded females lying
on nests (n = 7), while 85.5 ± 4.5% of photos (n = 2321) recorded
females in close attendance (∼2–8 m). Despite infrared function,
trap cameras were seldom activated at night (2.0% of all photographs)
due to high inactivity levels of females at nests. However,
46.4 ± 8.2% of our photographs that recorded females lying directly
on nests were captured at night, confirming high nocturnal fidelity
to nests. Cameras positioned <1.5 m from nest from 2011–2013
(n = 4) confirmed females move from the guarding position in close
proximity to the nest onto the actual nestitself during the late afternoon,
and then reverse this process in the early morning hours. For
one nest we could accurately determine the mean time the female
would move onto to the nest (18:29 ± 26.74 min, n = 39) and then
depart (06:07 ± 19.35 min, n = 15).
Aggressive defence by guarding Nile crocodile females in
response to non-human intruders at nest-sites was frequently captured
on camera, and appears to be a standard response to potential
or perceived nest predators. Camera position often precluded the
identity of the intruder, but females showed aggression toward egg
predators, mostfrequently water monitors. We recorded two types
ofthreat response behaviours from guarding Nile crocodile females
(Fig. 3); aggressive chasing/charging in response to water monitor
predation (Fig. 3a-b), and threatening mouth gaping in response
to nest disturbance (Fig. 3c-d). A single incident of intraspecific
aggression was recorded when a larger crocodile (likely a male)
entered a nesting area behind the guarding female. The female
quickly moved forward onto the nest. Six hours later the larger individual
was observed walking ∼4 m from the nest, which resulted
in a sudden aggressive response by the female in which she turned
180◦ to challenge the intruder, successfully scaring the crocodile
away from the nest.


Fig.3 Nile crocodile female nest defence at the Lake St Lucia estuarine system. The white arrow (a) indicates the direction of the stream, and the oval, the fresh excavation
marks on the nest. The white arrow (b) indicates the direction of the stream, and the oval, highlights a predated eggshell. The white arrow (c) indicates the shaded position
of the female, and the black oval, is the nest. The white arrow (d) indicates the direction the female is lying on the nest, and the white oval is the nest.

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