Monday, January 23, 2017

Ghost in the dunes--the cheetahs of the Sahara



"This is the sense of the desert hills: that there is room enough, and time enough."

-Mary Hunter Austin

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Evening, in the windswept dunes of southern Algeria, is a welcome affair. Somewhere in that fine line between day and night, the Saharan sun transforms from oppressively radiant taskmaster to beguiling friend. A steady breeze tosses about grains of sand, as though an hourglass was being slowly and imperceptively turned. As the desert sky fades from gold to blue, slow yet purposeful footsteps can be heard. A cheetah is on the prowl.



That there are populations of cheetahs living in the Sahara desert and its southernly neighbor, the Sahel, is only slightly less than the sum total of human knowledge of their ecology. Records of their numbers are slight, and few population surveys exist. But the little we do know paints a picture of an elusive, wide-ranging desert carnivore precariously holding onto existence by the slimmest margins.

The latest population surveys, compiled by Sarah Durant and colleagues in a 2017 paper, suggest that there approximately 220 North African cheetahs, of which 191 live in Algeria and Mali. The others exist in relict populations in Niger, Benin, and Burkina Faso. Of the core Algeria / Mali population, only 13% exist in protected areas. Because the chances of survival decline significantly outside protected regions without intensive management, any conservation strategy for the North African cheetah must focus on reducing conflict with the humans who share their land, and securing an ample prey base.

Behaviorally, this desert phantom is a near total enigma. Camera trap surveys indicate that unlike its southern cousins, who are mostly diurnal (day dwelling), North African cheetahs are most active during the night, when temperatures are lowest. Based on a survey of 35 cheetahs living in and around Ahaggar Cultural Park, Algeria, researchers suggested an average home range size of 1,583 square kilometers, an area 2.5 times larger than New York City.

Videos and photographs suggest that North African cheetahs are smaller and more lightly spotted than their southern cousins. Nothing is known about their feeding habits, prey requirements, or breeding ecology.

Due to this data vacuum, any information that we can gather is vital for the persistence of one of Earth's rarest, most endangered large mammals. That the cheetah can survive in a landscape as harsh and foreboding as the Sahara is testament to its incredible resolve and resiliency. And, given sufficient research and on-the-ground action, I remain hopeful that the sands will not whisper of the cheetah in memory alone.




Photo credit: Fraid Belbachir / ZSL / OPNA

References: 


Belbachir et al. 2015. Monitoring rarity: The critically endangered Saharan cheetah as a flagship species for a threatened ecosystem. PLos ONE 10(1):  http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0115136

Durant et al. 2017. The global decline of cheetah Acinonyx jubatus and what it means for conservation. PNAS 114(3): 528-533


Tuesday, June 23, 2015

When the mountain fears its deer: predators, trophic cascades, and ecological integrity - Part 1

"I have watched the face of many a newly wolfless mountain, and seen the south-facing slopes wrinkle with a maze of new deer trails. I have seen every edible bush and seedling browsed, first to anemic desuetude, and then to death. I have seen every edible tree defoliated to the height of a saddlehorn. Such a mountain looks as if someone had given God a new pruning shears, and forbidden Him all other exercise. … I now suspect that just as a deer herd lives in mortal fear of its wolves, so does a mountain live in mortal fear of its deer."

-Aldo Leopold

Our story begins in 1963, in a small bay that opens into the eastern Pacific Ocean. It's a rainy, gray day, of the kind that only an anxious and somewhat downtrodden coastal Washington can provide. The foamy seawater ripples with the eager anticipation of a coming storm. And, standing in a small rectangular enclosure, a man is fervently tossing starfish.

Pisaster ochraceus - purple sea star

Photo by Stephen Bensten.

In the Mukkaw Bay, the starfish Pisaster feeds on several species of barnacle. Where these starfish are present, the barnacles are restricted to a small band in the intertidal zone, outside of which one can find a litany of ocean dwellers, including anemones, chitons, limpets, algae, and sponges. To understand how Pisaster influences the structure of the tidal ecosystem, Robert T. Paine devised an experiment where seastars were removed from the enclosure, and the species living in the enclosure were monitored. Upon the predator's removal, barnacles surged in number, and crowded much of the available space. With the high barnacle population, the other intertidal species began to disappear. By controlling barnacle density, the sea star was the foundation of an entire intertidal ecosystem.

From this research, the keystone species concept was born.

Much as a keystone holds together an arch, a keystone species is one that disproportionately affects the other species in an ecosystem. When the keystone species is a predator, a 'trophic cascade' may occur, where species that the predator does not feed on change in abundance or behavior. While the concept of a trophic cascade can be simple, finding evidence for it is a surprisingly tricky endeavor. Ecosystems are complicated webs of interactions, and different parts are influenced by multiple factors. A barnacle is affected by predation, but also by weather, temperature, land use, and ocean acidity. These influences are further complicated by interactions: one effect may be stronger in the presence of another. For example, predation may affect a population more strongly when the weather is extreme than when times are calm.

In this upcoming series, I will be discussing a number of famous studies documenting trophic cascades across diverse ecosystems. I will describe the origins of the studies discovering the cascades, and the potential pitfalls of the available evidence. In a rapidly changing world, predators are an important component of the world's ecosystems, and I hope that this series of posts will inspire you and teach you about a key conservation concept.

Next week: sea otters, orcas, and shallow water ocean diversity 

Wednesday, June 10, 2015

A long time coming.

In a blinding flash, the universe came into being 13.82 billion years ago. Since that time, aeons have past. Elements were created; galaxies formed and galaxies lost. In the stellar turmoil, after 9 billion years, one planet in a corner of one of one hundred billion galaxies emerged.

On this planet, through little understood processes, life formed out of a swirling biochemical sea. With the help of natural selection and myriad random influences, life shaped itself into Darwin's 'endless forms most beautiful.' One species, a newcomer to the game of life, appeared in Africa 100,000 to 200,00 years ago. In its tenure on this planet, this species would stare into the vast chasm of extinction, and in its recovery spread 7 billion of its number to every continent on Earth. It shaped the planet to suit its needs. It was gifted sentience, and with it searched for meaning. Humans, as Carl Sagan once famously said, are 'a way for the universe to know itself.'

And it's this search for truth, a means to understand this world and its remarkable history, that drives me as a scientist. I want to learn. I need to learn.

But I want more. I want other humans to get a modicum of the awe and wonder that I receive in my wanderings about the natural world. I want them to channel that wonder into action; helping to restore wild places and create a relationship with wild things. I want them to appreciate their existence in this world.

And, to do that, I photograph, and I write.

Or at least I did.


Depression has a tendency to inspire inaction, and force its victim to revile the antidote. Recently, I've made a number of changes in my life on the road to mental recovery. One of those, the reason you are reading this today, is using writing to express my deeply felt wonder.

Consider this a promise to you, the reader, and to myself, that I will go on this written journey once again. And a journey, as they less frequently say, always begins with a single blog post.

Monday, June 18, 2012

The importance of reporting negative results in science--

"I have approximate answers and possible beliefs in different degrees of certainty about different things, but I'm not absolutely sure of anything, and of many things I don't know anything about, but I don't have to know an answer. I don't feel frightened by not knowing things, by being lost in the mysterious universe without having any purpose which is the way it really is as far as I can tell, possibly. It doesn't frighten me."

-Richard Feynman


Since its inception, one of the cornerstones of science has been the rigorous examination and scrutiny of claims about reality. Increasingly, scientists have developed a wide variety of statistical tools used to quantitatively analyze hypotheses about the world. These include the use of so-called probability values (a.k.a. 'p-values'), which allow for the formal evaluation of certain statistical hypotheses (e.g. whether there is any evidence that measured bill lengths of birds come from two different sample populations). Scientists have established a threshold for these probability values of 5%. To somewhat oversimplify, this indicates that when using p-values, we are willing to accept that an observed difference will be a false positive 5% of the time, or 1 time in 20 events. However, one of the common critiques of the use of p-values is that those analyses that fall outside of the 5% threshold are often unreported, especially in congruence with the pressure to report positive results in an effort to publish a given paper in a more prestigious journal. This, I feel, severely handicaps our ability to perform good science and best examine the world on its own terms. In fact, it may be that the publication of negative results is just what is needed to spur a scientific field forward into new theoretical realms.






For example, suppose that a researcher is interested in understanding how a variety of abiotic factors affect the reproduction of fish in a group of stream systems. Knowing what past research has been done on these areas, the researcher measures a variety of variables including stream temperature, nutrient quality, water velocity, etc. After determining that he has a sufficient sample size given the variability the researcher has seen in the data to properly detect effects if they exist, he runs a series of analyses and finds no significant results on any of the measured variables. The researcher is then met with a choice: scrap the whole analysis, continue to use new and possibly inappropriate statistical techniques until he finds a positive result, or report the negative results found by the analyses. It is the last option that I feel too few researchers choose, and also one that is often remarkably undervalued, because it's when our previous understanding of the likely causal drivers in these sorts of systems doesn't bear fruit that we are able to more fully develop our thinking and come up with new ideas of what is driving the behavior of these systems. For instance, there may be a species of invasive predator whose feeding habits strongly negatively influences the reproduction of the fish due to heavy levels or predation or increased stress levels and their associated decrease in fecundity. If researchers do not report on these sorts of negative results, the ecological 'man behind the curtain' may never be seen otherwise.

Beyond other unfortunate effects inherent in the lack of reporting of negative results (e.g. biased meta-analyses, which are used to synthesize information across many published studies), I feel that the avoidance of publishing negative results is a ready recipe for scientific stasis, and that it would best suit science if it was stopped altogether. There are many social factors that make this difficult (e.g. the career pressure to publish in high impact journals, which is most readily done when a researcher has significant positive results to discuss), but I think that science as a whole would be supremely benefited in the long run if the trend was bucked.

Sunday, May 20, 2012

Field season imminent--

In two days, I will begin the trip to Yaak, Montana to begin training for my position as an assistant technician for the Cabinet-Yaak Grizzly Bear DNA Project, collecting grizzly bear (and other) hair from strategically placed snares throughout an extensive study area.

I will be paid for outdoors adventure and science. This pleases me.

Saturday, April 28, 2012

Non-comprehensive list of links on wildlife biology and ecology--


This list will be sporatically updated over time. Enjoy.


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Blog articles on ecology and science as a career:









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Blog posts from wildlife biologists in the field doing what wildlife biologists do:


























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Other posts related to wildlife biology and ecology:



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Yale ecology lectures:

1. The nature of evolution: selection, inheritance, and history


2. Basic transmission genetics


3. Adaptive evolution: natural selection


4. Neutral evolution: genetic drift


5. How selection changes the genetic composition of populations


6. The origin and maintenance of genetic variation


7. The importance of development in evolution


8. The expression of variation: reaction norms


9. The evolution of sex


10. Genomic conflict


11. Life history evolution


12. Sex allocation


13. Sexual selection


14. Species and speciation


15. Phylogeny and systematics


16. Comparative methods: trees, maps, and traits


17. Key events in evolution


18. Major events in the geological theatre


19. The fossil record and life's history


20. Coevolution


21. Evolutionary medicine


22. The impact of evolutionary thought on the social sciences


23. The logic of science


24. Climate and the distribution of life on Earth


25. Interactions with the physical environment


26. Population growth: density effects


27. Interspecific competition


28. Ecological communities


29. Island biogeography and invasive species


30. Energy and matter in ecosystems


31. Why so many species? The factors affecting biodiversity


32. Economic decisions for the foraging individual


33. Evolutionary game theory: fighting and contests


34. Mating systems and parental care


35. Alternative breeding strategies


36. Selfishness and altruism


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Other talks on wildlife biology and/or conservation:

E.O. Wilson on saving life on Earth


Corneille Ewango is a hero of the Congo forest


Alan Rabinowitz: Saving big cats


John Kasaona: how poachers became caretakers



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Wildlife documentaries:

In search of the jaguar:


Lost land of the tiger:

Wednesday, April 18, 2012

Unusual deaths amongst the Felidae--

Few organisms are as often associated with grace, grandeur, and grit as those belonging to the Felidae. And, so much as they can be said to hold those traits in life, so too may they may hold them in death. However, being wild animals that are frequently exposed to a wide variety of often unpredictable conditions, they may be met with a demise that is somewhat unbecoming of their notoriously feral reputation. 

Two such instances were reported by Frank Nicholls in the Journal of the Bombay Natural History Society in the early 1950s.


Imagine, if you will, that you are in the jungles of India. The temperature is sweltering, and the humidity is complimentarily oppressive. You yawn and stretch, taking a break from the seemingly never-ending trail that you have been following, and see a woman walking towards a stone well. Pleased to have some degree of human company, you saunter towards her, but you quickly pause when you hear the sharp snap of a twig.  Looking for the source of the unexpected sound, your eyes are drawn to a nearby cluster of vegetation, and are met with the face of the most iconic organism in all of India. 


The tiger lunges forward with such speed and ferocity that you are rendered speechless. It seems to close the gap between the woman and itself in an instant, and leaps into the air towards her. By some great stroke of luck, the woman bends down to retrieve some much-needed water from the well. And, to the tiger's misfortune (and your own astonishment), you see the tiger plunge into the well and out of sight.


 
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The next day, while wandering a nearby labor camp, you hear a great commotion, as though though a lion were caught in a blender mid-roar. You run towards the unnerving cacophony, and see a leopard lying on its side, with a pile of blood pooled immediately in front of him. 



As you lower yourself for a closer look, you gasp in astonishment. Inside the leopard's mouth, as still as the leopard itself, you see the back half of a domestic cat. As well as you can surmise, the leopard had attempted to predate upon the fierce creature, and had been killed by it while it was struggling for survival inside its gaping maw.