Cabins are seen at the exclusive Meno a Kwena Lodge near Maun in the Okavango Delta, Botswana, April 24, 2018. Picture taken April 24, 2018. REUTERS/Mike Hutchings

Trees stand on islands as water begins to fill the Okavango Delta, Botswana, April 24, 2018. Picture taken April 24, 2018. REUTERS/Mike Hutchings

A herd of zebras is seen in the Okavango Delta, Botswana, April 25, 2018. REUTERS/Mike Hutchings

The shadow of a small aircraft is seen as water begins to fill the Okavango Delta, Botswana, April 24, 2018. Picture taken April 24, 2018. REUTERS/Mike Hutchings

Reeds sit as waters begins to fill the Okavango Delta, Botswana, April 24, 2018. Picture taken April 24, 2018. REUTERS/Mike Hutchings

Trees stand on islands as water begins to fill the Okavango Delta, Botswana, April 24, 2018. Picture taken April 24, 2018. REUTERS/Mike Hutchings

A fire greets visitors at the exclusive Mapula Lodge in the Okavango Delta, Botswana, April 24, 2018. Picture taken April 24, 2018. REUTERS/Mike Hutchings

Trees stand on islands as water begins to fill the Okavango Delta, Botswana, April 24, 2018. Picture taken April 24, 2018. REUTERS/Mike Hutchings

A startled antelope jumps over a baboon in the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

The sun rises behind a Baobab tree in the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

The sun rises behind a Baobab tree in the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

A startled antelope jumps over grassland in the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

A young bull elephant is seen in the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

A pod of hippos is seen in the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

Trees stand on islands as water begins to fill the Okavango Delta, Botswana, April 26, 2018. Picture taken April 26, 2018. REUTERS/Mike Hutchings

Trees stand on islands as water begins to fill the Okavango Delta, Botswana, April 26, 2018. Picture taken April 26, 2018. REUTERS/Mike Hutchings

Reeds sit as waters begin to fill the Okavango Delta, Botswana, April 24, 2018. Picture taken April 24, 2018. REUTERS/Mike Hutchings

Guests stand beneath a Baobab tree illuminated by fire in the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

A pair of male elephants is seen in the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

The exclusive Mapula Lodge is seen in the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

The sun sets over the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

A cabin is seen at the exclusive Mapula Lodge in the Okavango Delta, Botswana, April 26, 2018. Picture taken April 26, 2018. REUTERS/Mike Hutchings

The sun sets over the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

The exclusive Mapula Lodge is seen in the Okavango Delta, Botswana, April 26, 2018. Picture taken April 26, 2018. REUTERS/Mike Hutchings

Cabins are seen at the exclusive Mapula Lodge in the Okavango Delta, Botswana, April 26, 2018. Picture taken April 26, 2018. REUTERS/Mike Hutchings

Cabins are seen at the exclusive Mapula Lodge in the Okavango Delta, Botswana, April 26, 2018. Picture taken April 26, 2018. REUTERS/Mike Hutchings

A fisherman reels in a catfish in the Okavango Delta, Botswana, April 24, 2018. Picture taken April 24, 2018. REUTERS/Mike Hutchings

A fish eagle sits above waters flowing into the Okavango Delta, Botswana, April 24, 2018. Picture taken April 24, 2018. REUTERS/Mike Hutchings

Plants float in the waters of the Okavango Delta, Botswana, April 24, 2018. Picture taken April 24, 2018. REUTERS/Mike Hutchings

The sun sets over the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

The sun sets over the Okavango Delta, Botswana, April 25, 2018. Picture taken April 25, 2018. REUTERS/Mike Hutchings

A large robot nicknamed ÒKongÓ lifts the body of a Ford Expedition SUV at FordÕs Kentucky Truck Plant as the No. 2 U.S. automaker ramps up production of two large SUV models in Louisville, Kentucky, U.S., February 9, 2018. Picture taken on February 9, 2018. REUTERS/Nick Carey

A large robot nicknamed ÒKongÓ lifts the body of a Ford Expedition SUV at FordÕs Kentucky Truck Plant as the No. 2 U.S. automaker ramps up production of two large SUV models in Louisville, Kentucky, U.S., February 9, 2018. Picture taken on February 9, 2018. REUTERS/Nick Carey

Saskatchewan Roughriders running back Jerome Messam (C) is tackled by Toronto Argonauts defensive back Vincent Agnew (R) and Toronto Argonauts defensive lineman Tristan Okpalaugo (L) during the second half of their CFL football game in Regina, Saskatchewan July 5, 2015. The Toronto Argonauts defeated the Saskatchewan Roughriders 42-40. REUTERS/Matt Smith TPX IMAGES OF THE DAY

Winnipeg Blue Bombers quarterback Drew Willy is sacked by Toronto Argonauts' Tristan Okpalaugo and Dwight Anderson in the fourth quarter of their CFL football game in Toronto August 12, 2014. REUTERS/Fred Thornhill (CANADA - Tags: SPORT FOOTBALL)

Winnipeg Blue Bombers quarterback Drew Willy is sacked by Toronto Argonauts' Tristan Okpalaugo (L) in the first half of their CFL football game in Toronto August 12, 2014. REUTERS/Fred Thornhill (CANADA - Tags: SPORT FOOTBALL)

Nicholas Okongo Okoth of Kenya (L) is punched by Alfonse Deireragea of Nauru during their men's light welterweight fight at the 2014 Commonwealth Games in Glasgow, Scotland, July 27, 2014. REUTERS/Phil Noble (BRITAIN - Tags: SPORT BOXING)

Saskatchewan Roughriders quarterback Darian Durant (R) gets away from Toronto Argonauts defensive lineman Tristan Okpalaugo during the second half of their CFL football game in Regina, Saskatchewan July 26, 2014. The Roughriders won the game 37-9. REUTERS/David Stobbe (CANADA - Tags: SPORT FOOTBALL)

Saskatchewan Roughriders quarterback Darian Durant runs in a touch down while getting chased by Toronto Argonauts defensive lineman Tristan Okpalaugo (L) during the first half of their CFL football game in Regina, Saskatchewan July 26, 2014. REUTERS/David Stobbe (CANADA - Tags: SPORT FOOTBALL)

Ottawa Redblacks' quarterback Henry Burris runs under pressure from Toronto Argonauts' Tristan Okpalaugo during the first half of their CFL football game in Ottawa July 18, 2014. REUTERS/Chris Wattie (CANADA - Tags: SPORT FOOTBALL)

Team USA pose for a team photo before their CONCACAF Olympic qualifying soccer match against El Salvador in Nashville March 26, 2012. Pictured front row from left:
Amobi Okugo (16), Kofi Sarkodie (3), Jorge Villafana (13), Freddy Adu (7), Joe Corona (10).
Back from left:
Bill Hamid (1), Ike Opara (2), Perry Kitchen (4), Terrence Boyd (15), Mix Diskerud (8), Brek Shea (11).
REUTERS/Harrison McClary (UNITED STATES - Tags: SPORT SOCCER OLYMPICS)

Real Madrid's Fabio Coentrao (R) is challenged by Philadelphia Union's Amobi Okugo during their World Football Challenge friendly soccer match in Philadelphia, Pennsylvania, July 23, 2011. REUTERS/Tim Shaffer (UNITED STATES - Tags: SPORT SOCCER)

Filmmakers Dereck and Beverly Joubert (R) pose after an interview with Reuters in New York, February 18, 2011. The husband and wife team are somewhat famous in the small world of wildlife documentaries, and to those outside it, lead a romantic life filming wild animals against an enchanting African landscape, but the topic of their new film, "The Last Lions," which recently opened in the United States, is anything but ideal.
The cold statistic that drew the Jouberts to their latest story -- set in the lush wetlands of Botswana's Okavango Delta -- speaks for itself.
In the last 50 years, African lions have plummeted in numbers from 450,000 to between 20,000 and 50,000, conservation groups say. Picture taken February 18, 2011. REUTERS/Brendan McDermid (UNITED STATES - Tags: ENTERTAINMENT ENVIRONMENT ANIMALS)

Filmmakers Dereck and Beverly Joubert (R) pose after an interview with Reuters in New York, February 18, 2011. The husband and wife team are somewhat famous in the small world of wildlife documentaries, and to those outside it, lead a romantic life filming wild animals against an enchanting African landscape, but the topic of their new film, "The Last Lions," which recently opened in the United States, is anything but ideal.
The cold statistic that drew the Jouberts to their latest story -- set in the lush wetlands of Botswana's Okavango Delta -- speaks for itself.
In the last 50 years, African lions have plummeted in numbers from 450,000 to between 20,000 and 50,000, conservation groups say. Picture taken February 18, 2011. REUTERS/Brendan McDermid (UNITED STATES - Tags: ENTERTAINMENT ENVIRONMENT ANIMALS)

Philadelphia Union midfielder Amobi Okugo (L) battles for the ball with Toronto FC midfielder Nick LaBrocca (R) during the first half of their MLS soccer match in Chester, Pennsylvania, July 17, 2010. REUTERS/Tim Shaffer (UNITED STATES - Tags: SPORT SOCCER)

Scotland's Ben Werv (C) breaks for the tryline past Kenya's David Okwego (R) and Felix Ochiengo during their quarter-finals rugby match in the IRB Sevens tournament in George, South Africa December 10, 2005. Scotland won the match 36-5. REUTERS/Howard Burditt

A male African white Heron flies in the Okavango Delta in Botswana March 26, 2005.

A male African Pied Kingfisher on a reed in the Okavango Delta in Botswana March 26, 2005.

A African fish eagle flies in the Okavango Delta in Botswana March 26, 2005.

A male African fish eagle flies in the Okavango Delta in Botswana March 26, 2005.

An African fish eagle flies in the Okavango Delta in Botswana March 26, 2005. REUTERS/Thomas White TW

A male African Great White Egret flies in the Okavango Delta in Botswana March 26, 2005. REUTERS/Thomas White TW

A male African Pied Kingfisher on a reed in the Okavango Delta in Botswana March 26, 2005. REUTERS/Thomas White TW

A male African fish eagle flies in the Okavango Delta in Botswana March 26, 2005. REUTERS/Thomas White TW

A male African elephant mock-charges in the Okavango Delta in Botswana March 25, 2005. REUTERS/Thomas White TW

A male African lion runs while hunting in the Okavango Delta in Botswana March 25, 2005. REUTERS/Thomas White TW

Aerial view of ring where Swiss wrestlers Adrian Leimbacher and Reto Maurer fight during the Federal Wrestling Festival in Lucerne, August 21, 2004. 130 Swiss-style wrestlers, or ôSchwinger" will go on to compete for a crown and other prizes, worth 500,000 Swiss francs (403,000 U.S. dollars) on Sunday, the overall winner, the ôkingö, will receive a bull. REUTERS/Sebastian Derungs