Living on Fish

A while ago I offered a post on some of the huge number of bird species that live by eating insects; the numbers involved are staggering. At least equally so, and in terms of sheer mass probably more so, are the numbers of animals that live wholly or significantly on fish. Mostly I'll be talking about birds again, but not entirely. 

Pied Kingfisher Ceryle rudis, Queen Elizabeth NP, Uganda.

The fish resource, though severely depleted by human overfishing, is extraordinary. One authoritative source puts the annual human wild fish catch at 90-95 million tonnes. It's hard to imagine that in terms of numbers of fish, and of course many animals take fish smaller than those generally consumed by people.

Moreover fish is a food high in energy and protein, so energy-consuming hunting strategies can be profitably applied. The Pied Kingfisher above could well have caught his lunch (and it is a he, with that broad breast band) by hovering, which burns lots of energy. 

Pied Kingfisher hovering, Amboseli NP, Kenya.

Many birds plunge into the water from above, or swim on the surface then dive, and pursue the fish underwater, a high energy game indeed. Many of these birds hunt in flocks, which are sometimes vast, converging on schools of fish which can number millions of potential prey items. To encounter such a hunt is among the most dramatic spectacles nature can afford us.

Cormorants (several species) converging on a huge fish school, Humboldt Current, northern Chile.
This is only a small part of the vast loose flock that streamed out to sea in response to other
birds already there.

Kelp Gulls Larus dominicanus and Black-browed Albatross Thalassarche melanophris in the
Strait of Magellan; upwelling cold waters provide the richest fisheries.

Blue-footed Boobies Sula nebouxii (again a tiny part of a flock of hundreds) smashing into the water
from tens of metres up, Galápagos. Note how they close their wings just before they hit the
water. They have no nostrils, which would be a serious disadvantage here.

Peruvian Pelicans Pelecanus thagus diving, Isla de Chiloé, southern Chile.

To an Australian, seeing the two big brown American pelicans diving from on high is a real surprise. Australian pelicans (which are bigger), hunt by swimming, then dipping their huge bills with elastic pouch into the water. They too often hunt in flocks however, chasing the fish schools, often accompanied by cormorants.

Australian Pelicans Pelecanus conspicillatus and Pied Cormorants Phalacrocorax varius,
Longreach Waterhole near Elliott, Northern Territory.

Australian Pelicans fishing, Canberra. The water here is shallow so they had to turn their
heads side on to submerge them. They scoop up water in the bill pouch and squeeze it out, retaining
fish and other prey items.     

 

Pelicans waiting for fish - sometimes stunned by the turbulence - to come through the lock
at Blanchetown on the River Murray, South Australia. The resting cormorants are
presumably sated; you can catch enough fish to fill your energy needs in
a relatively short time.

The cormorants benefit from the fish stirred up by the bigger birds, and will even snatch fish from the corners of a pelican's beak. They of course do pursue the fish underwater.

Little Black Cormorants Phalacrocorax sulcirostris, fishing in Kinchega NP,
western New South Wales.

Fish are slippery - they have an antibiotic surface slime and very smooth scales for sliding efficiently through the water - so a specialised bill is required. Cormorant bills are strongly hooked.

Little Black Cormorant, Coffs Harbour, NSW.
You'll see the hook better if you click on the picture to enlarge it.

Penguins and petrels and shearwaters have similar hooks.

Flesh-footed Shearwaters Ardenna carneipes, Lord Howe Island.

However many effective fish-eaters do not. Darters - a group of four diving fishers superficially resembling cormorants - tend to stalk along the bottom and ambush their prey rather than actively pursuing it like a cormorant. They have sharp-tipped bills and tend to stab upwards, surfacing and swallowing the stricken fish head-first.

Female Australian Darter Anhinga novaehollandiae with fish.
The weird kink in the neck is due to a hinge between the eighth and ninth
cervical vertebrae which enables the bird to thrust its neck forward like a spear.
The bill actually has little serrations on the inner edges to assist in swallowing.

This can be seen better in other species, including these Royal Spoonbills Platalea regia.

Royal Spoonbills at Jerrabomberra Wetlands, Canberra. The one on the left is swallowing a small fish.
Below you can see the bill serrations if you click on the photo.

These spoonbills are hunting primarily by touch by means of a 'bill tip organ' comprising many thousands of tightly packed sensors both in the tip of the bill and in the upper and lower jaws. These combine touch and taste and cause the bill to snap shut if it encounters something edible. Many birds which hunt food in mud and muddy water have such sensors.

Wood Storks Mycteria americana, Pantanal, south-eastern Brazil.

The really big storks have such organs too, but often their fish prey is so big that they can rely on their vision.

Jabiru Jabiru mycteria with big fish, Pantanal.
Despite the bird's huge size, it struggled for a long time to subdue and swallow this mighty meal.
However I doubt that it needed another one that day!

Saddle-billed Stork Ephippiorhynchus senegalensis, with big catfish (I think),
Amboseli NP, Kenya.

A slightly different use of the bill-tip organ is applied by the fascinating skimmers, three distinctive species in the gull and tern family. Their bottom mandible is much longer than the upper. They fly along the water surface trailing the tip of the bottom one in the water and when it encounters a fish or other food item the bill snaps shut on it.

Black Skimmers Rynchops niger;
Pantanal above, and Isla de Chiloé, southern Chile, below.

Fish-eating birds of prey - fishing eagles, ospreys and even fishing owls - certainly have an appropriate hooked bill, but in fact they inherited that, ready evolved, from non-fishing ancestors. They catch their fish using powerful clawed feet.

Eastern Osprey Pandion cristatus, Hervey Bay, Queensland.
The two closely-related osprey species are found all over the world; they are the only
day-time birds of prey to be exclusively fish eaters. Their large back-hooked claws
differ from those of most fishing eagles, and are adapted to slippery fish.

White-bellied Sea Eagle Haliaeetus leucogaster carrying fish dinner,
Port Macquarie, NSW.

African Fish Eagle Haliaeetus vocifer, Queen Elizabeth NP, Uganda.
The ten species of fishing eagle, found across the globe, are now
regarded as all being in the one genus. Though the claws aren't hooked,
the power of the feet is evident in this photo.

Grey-headed Fish Eagle Haliaeetus ichthyaetu, Sabah, Malaysian Borneo.
Until recently this and another species were regarded as separate from the other
fish eagles; they are even more fish-reliant than the others and it is no coincidence
that they have oprey-like recurved claws.

Fishing owls are found both in Africa and Asia, with three species each; the two groups are quite separate and the African ones differ in being almost exclusively fish-reliant.

Buffy Fish Owl Ketupa ketupu, Kinabatangan River, Sabah.
The African fishing owls plunge their legs into the water like fishing eagles,
but the Asian ones are more fastidious, not liking to get their feathers wet.

The many species of abundant gulls, all over the world, do catch fish, but they also scavenge many fish carcases; these days of course many of these are due to discards from human fishing.

Pacific Gull Larus pacificus, Esperance, Western Australia.

Silver Gull Chroicocephalus novaehollandiae, Cairns, north Queensland.

Many marine mammals (especially seals, sea lions and toothed whales) and some freshwater ones are fish eaters. Of these some of the best-known and most specialised are the otters, a group of highly specialised aquatic weasels, some of them quite large. 

The magnificent Giant Otter Pteronura brasiliensis, here in the Pantanal of Brazil,
showing its beautifully adapted paddle-shaped tail.

Giant Otters sharing - and squabbling over - fish in the Manu section
of Peruvian Amazonia. These two areas are relative strongholds of this superb animal,
which can grow up to 2.5 metres long and weigh over 30kg. Populations though are
tragically depleted by illegal hunting for its fur. They are strongly gregarious.

Neotropical Otter Lontra longicaudis, Pantanal, in a roadside lagoon.
About half the size of the Giant Otter and solitary, it is not well known.

The Marine Otter Lontra felina, here off the Isla de Chiloé, southern Chile,
is rare and is also poorly understood. It is quite different from the
Sea Otter of North America.

There are fish-eating reptiles, most notably crocodilians, all of which eat a lot of fish; some eat little or nothing else.

Yacaré Caiman Caiman yacare with substantial fish lunch, Pantanal.

And there are even some fish-eating invertebrates, from sea anemones to insects such as giant water bugs and dragonfly larvae, to spiders. The genus of big fishing spiders, Dolomedes, is found across the world. The long-legged spiders run across the water surface where they seize and deliver a venomous bite to fish and invertebrates.

Fishing spiders in Yasuní NP, Ecuadorian Amazonia above,
and southern Sarawak, Malaysian Borneo, below.

If you like fish, you're not alone. Hopefully this post might have offered you a broader perspective on the fish dinner.

Ringed Kingfisher Megaceryle torquata with fish, Pantanal.

NEXT POSTING THURSDAY 15 JULY

I love to receive your comments and in future will be notifying you personally by email when a new posting appears, if you'd like me to. All current subscribers have been added to this mailing list and have already been contacted.
This will mean one email every three weeks at the current rate of posting. 

I promise never to use the list for any other purpose and will never share it.
Should you wish to be added to it, just send me an email at calochilus51@internode.on.net.
You can ask to be removed from the list at any time,
or could simply mark an email as Spam, so you won't see future ones.

Thank you!

Serengeti Sublime; #1 landscapes and mammals

I suppose every naturalist has a wish list of places we really want to see elsewhere in the world. Mine began to develop at a fairly young age, and is pretty predictable, fuelled by wildlife documentaries (thank you Sir David!!) and books. They include the Galápagos, Amazon basin, Pantanal, Borneo rainforests, Madagascar, Okavango Delta, central African rainforests - and the Serengeti-Ngorongoro Crater-Masai Mara system of Tanzania and Kenya. Over the last decade or so I've been incredibly lucky with this list, and just last year we got to spend some time in the last of them. 

The Serengeti - usually translated from the Masai as meaning 'endless plain' - is a vast park of rolling woodlands and grasslands in northern Tanzania. In 1981 it was declared a UNESCO World Heritage Site. It covers some 1.5 million hectares but, with the connected parks, this becomes three million hectares of protected land, supporting one of the greatest wildlife concentrations, and thus spectacles, in the world.

This (fairly low resolution) map, courtesy of the excellent Natural World Heritage Sites website,
indicates the location of Serengeti (red) in Tanzania and in Africa.

This map (courtesy Mahlatini) shows the entire Serengeti ecosystem of parks and 
the annual route of the great permanent circular migration of large grazing mammals,
dominated by Blue Wildebeest, following the rains and the grasses.

Blue Wildebeest Connochaetes taurinus and calf, with a glimpse of part of the herd behind.
Figures vary with sources, but UNESCO reports some two million wildebeest, 900,000 Thomson's and Grant's Gazelles,
200,000 Plains Zebras and (relatively!) smaller numbers of other herbivores walk the 1,000km circuit every year.

Inevitably the herds are accompanied by large numbers of carnivores, including
3,500 Spotted Hyenas Crocuta crocuta (according to UNESCO, though other sources
cite figures of twice this). These were part of a larger group which was showing a lot
of interest in the passing herds.

But before introducing more of the park's animals to you, let's set the scene by looking more at the landscapes, which are truly grand, and a very brief history. The Maasai people arrived from South Sudan and northern Kenya in the 18th century, displacing existing inhabitants. They were herders, with cattle being (then and now) fundamental to their culture and economy. Maasai villages are scattered in the Ngorongoro Conservation area (see map above) and cattle, goats and donkeys are herded on the hills there. 

Perhaps surprisingly the first European in the area was the impressive young Austrian explorer and map-maker Oscar Baumann as late as 1892. (He later also became the first European to enter the Ngorongoro Crater and climb Mt Kilimanjaro.) He was followed in 1913 by a very different person, US novelist, spiritualist (he reckoned the spirits sent him the ideas for his books) and enthusiastic slaughterer of wildlife for entertainment, Stewart Edward White. On his first trip he marvelled at the abundance of mammals (or 'game' as he preferred); his great realisation from this wonder was that "no sportsman’s rifle has ever been fired" at them. He hastened to rectify that omission.

The country near Seronera, much as White saw it.
The dominant trees here are Fever Trees Vachellia (Acacia) xanthophloea.

In the following decade he returned with equally enthusiastic friends, and proceeded to wantonly kill over 50 lions just in the area around Seronera, now the park administrative and interpretive headquarters. This amusement became so popular that the British Administration eventually stepped in (presumably to ensure there were still some lions for them to shoot) and declared a 'partial game reserve' - though what 320ha was going to protect is not at all clear.

In the end a full national park was declared in 1951. The Ikoma hunters were moved to the north of the park where they became farmers and are seemingly not too dissatisfied. The Maasai on the other hand were moved to what was promised as good grazing lands, but instead turned out to be hard arid country around Oldupai Gorge to the east. Their situation is not so good, as we observed ourselves. I am not qualified to comment further on this but it would be remiss to ignore this aspect.

Mention should be made of the Grzimeks, German zoologists and conservationists, father and son, Bernard and Michael, who studied and made pioneering documentaries about Serengeti and introduced it to the world. The park, as I mentioned earlier, was declared a World Heritage Site in 1981.

It comprises woodland and grassland; we spent most of our time in the south-east of the park where the short grasses dominate. 

This was taken from the moving vehicle; the wildebeest and hyena photos above probably
give a better idea of the short grass plains.

Acacia thorntree grassy woodland. If you expand the photo by clicking on it you can see
the big herds in the distance.

Fever Trees again; I'm a fan, probably sparked by reading Kipling all those years ago.
(And if you don't recognise the reference, have a look at The Elephant's Child.)

And an important habitat component, though quite a small one in area, are the koppies, huge tumbled piles of igneous rock that rise from the plains.

Koppie with Candelabra Euphorbia C. candelabrum in the foreground.
And spot the Leopard!

To make it easier, here's a closer photo of this magnificent male, resting but very aware of his surroundings. 

Not my first Leopard, but by far my best ever view.
There an estimated 1,000 Leopards in Serengeti.

Interestingly he was sharing the outcrop - more of a small mountain really - with a big male Lion; we found it hard to imagine that they were unaware of each other but they were a couple of hundred metres apart. While Lions can do kill and eat even adult Leopards, they both probably knew that he couldn't get near the Leopard undetected.

Adult male Lion in the sparse shade of a small fig tree.
While we didn't see many lions on this occasion, there are reportedly some 3000 in the park.
This would represent about a third of Tanzania's population, which in turn holds
perhaps half of the world's wild Lions.

Even this wasn't the end of the cats however, including two of the rare and difficult to see ones.

In the end we saw Cheetahs in four parks across Tanzania and Kenya, but none better than this lovely male.
He is one of about 225 Cheetahs in Serengeti.

I'd never seen a Cheetah before, but an even rarer sighting is the smaller long-legged Serval, a hunter of rodents, birds and reptiles in long grass.

Serval Leptailurus serval taking a break from stalking lunch.

Even smaller hunters were out and about too, mostly after insects, spiders, scorpions, rodents and small reptiles.

Dwarf Mongooses Helogale parvula, only about 25cm long, hunt in families.

But of course there are many more herbivores than carnivores in Serengeti, as everywhere. Elephants are evident on the plains.

This was part of a file of 11 Elephants marching calmly but purposefully across the plain,
led as usual by an old cow...

... with an even older one with big tusks, one at an angle, bringing up the rear.

And I know it's absurd, but here is an elephant's closest living (non-elephant) relation - along with manatees and dugongs! OK, they haven't been connected for about 50 million years, but they're still closer to each other than to anything else.

Rock Hyrax Procavia capensis relaxing in the shade on a hot day.

Giraffes - here the Masai subspecies (or maybe even species, see here) - are spread throughout the park.

Masai Giraffes are characterised by 'splintered' spots that extend down the legs.

Their lips and tongue are seemingly impervious to acacia thorns, which can be wicked by our standards.

There are hippos in the waterways, though we didn't see many compared with other mammals, and with other places.

Male hippos can do appalling damage to each other in conflict, but these two weren't very serious -
possibly young males practising.

Antelope are the most conspicuous mammal group in the park, not only because of the huge numbers of wildebeest mentioned earlier. Here are a few more of them.

Topi Damaliscus jimela (sometimes still regarded as a subspecies of Tsessebee D. lunatus).
A big quick antelope found across central east Africa.

Female Waterbuck Kobus ellipsiprymnus; this is the northern subspecies known as Defassa Waterbuck.
While they will readily take to water to avoid predators, it's not otherwise part of their habitat.

Thomson's Gazelle Eudorcas thomsonii, one of two abundant gazelles in Serengeti,
and an important part of Cheetahs' diets.

Bohor Reedbuck Redunca redunca, a small antelope found across central Africa.

Kirk's Dik-dik Madoqua kirkii, a tiny antelope (though the largest dik-dik) widespread in the Serengeti.
This one was seen from the balcony of our lodge room.

Male Vervet Monkey Chlorocebus pygerythrus flaunting his most striking attribute.
An abundant ground-foraging monkey found throughout East Africa and much of South Africa.

A seemingly more demure Vervet, though this one was plotting how to get into our room.
Fortunately we were onto him.

Another appealing feature of our lodge accommodation was the colony of little Wahlberg’s Epauletted Fruit Bats roosting in the low trees in the courtyard.

And I know these last two beauties aren't mammals, but I couldn't very well leave them out, could I!?

Young Leopard Tortoise Stigmochelys pardalis; when it's older its lovely shell will become duller.
A large tortoise found across much of eastern and southern Africa.

Nile Crocodile Crocodylus niloticus (with Three-banded Plover); the Serengeti rivers
run ultimately into Lake Victoria, and I don't doubt that crocodiles move to and from
there on occasions.

So, there's a brief introduction to one of the world's great parks; next time I'll introduce you to some of the numerous and wonderful birds of Serengeti. And when we can travel again, you really should move on from just thinking about going there...

NEXT POSTING THURSDAY 14 MAY.
And remember that you can get a reminder when the next post appears by putting your email address in the Follow by Email box in the top right of this screen.
I'd love to receive your comments - it's easy and you don't need to sign in!