You’ll have to forgive me if I am less eloquent than I’d like to be. It’s late Sunday night, and my brain is still reeling from one of the most intellectually exciting and intense weeks I think my Ph.D. career has seen.

Right. So. Craig, Meredith, and I spent the last week at the first ever Gordon Research Conference on Predator-Prey Interactions. It was quite the meeting-of-the-minds for ecologists, and I spent much of the week rather star-struck.  See, while much of our scientific careers are spent collecting, cleaning, and analyzing data (not to mention trying to convince funding agencies that they should give us money), a significant portion of our time also goes towards pouring over the thoughts, insights, and experiences of other researchers as they are articulated in scientific journal articles. We are impressed and sometimes awed by their insight. Our own scientific aspirations are shaped by their creativity and vision.

At the GRC last week, I had a chance to meet the movers and shakers who fundamentally shape the way that we ecologists see the world around us…and it was awesome.

Dr. Jim Estes, a professor at UC Santa Cruz, was one of these movers and shakers. Dr. Estes is perhaps best known for his work on sea otters that provided one of the first and most spectacular examples of how a keystone predator could shape an entire ecosystem. A keystone predator is one that plays a crucial role in the larger community, and whose disappearance has disproportionate and dramatic consequences that cascade throughout the ecosystem in what we call a trophic cascade. (“Trophic” refers to different levels within the food web.)

A pacific northwest ecosystem with and without sea otters. From the recently published Ripple et al. (2014) Science article.

When sea otters disappear from pockets of oceans in the Pacific northwest,  the number of sea urchins (which otters love to eat) increases. And sea urchins increase a lot. Without the otters to keep sea urchins in check, the urchins eat up all of the kelp that many fish, crabs, and other underwater sea creatures call home. No otters means no kelp, and no kelp means that a vast array of other underwater sea creatures also disappear.

Otters were recognized as keystone predators back in the 1970’s. But they aren’t the only carnivore that can change the face of an ecosystem. In fact, Dr. Estes presented a “sneak peak” at results from a  review paper that he and colleagues were just about to publish in one of the world’s leading scientific journals.

Their article documents that at least seven of the world’s 31 large carnivores have been found to trigger trophic cascades. Some of these effects derive from the fact that big predators reduce herbivores by eating them. But some of these effects are mediated through “fear” — in which prey animals change their behavior to avoid predation. And some of these changes are because top predators suppress smaller predators, which in turn suppress their prey.

There are many, many ways in which top predators shape the face of ecosystems around the world. Furthermore, as Dr. Estes and his colleagues (all “biocelebrities” and many of whom were also at the GRC!) point out in this new paper, these top predator populations are declining. They are declining quickly and globally, and they are declining as a result of human disturbance. What’s worse is that even though we know that these top predators can have enormous influence over the structure and function of natural systems, we don’t really understand the general patterns that underlie their influence. So as they disappear, it’s anyone’s guess as to how our natural places will change.

It’s abundantly and urgently clear from the recent scientific literature and from the thoughts and interests of ecology’s biggest names at last weeks’ conference that we need to understand how top predators shape the natural world. I’m hopeful that our research here at Snapshot Serengeti will continue to provide tiny pieces of the puzzle towards this scientific understanding. Thank you guys for helping us understand how this amazing world works.

Sorry for the silence, everyone. Craig, Meredith, and I are currently neck deep in the first ever Gordon Research Conference on Predator Prey Interactions. 

We are busy trying to sound intelligent and trying not to be too “star struck.” Yes, believe it or not, there are “bio-celebrities.”

Today I’m hosting a break-out session on the role of “fear” in predator-predator coexistence — wish me luck and I’ll tell you all about it next week!

It’s a new year. Of course, I am in blatant denial about this, since this means time is passing and I haven’t finished all of the things I planned to do in 2013, but the calendar has turned despite my protests.

So happy 2014 everyone! Here’s a few of the awesome photos we’ve collected over the last year. I’m looking forward to collecting newer and better ones in the year to come!

these guys will always be my favorite animals.

well hello.

heehee.

baby!

hi.

As pretty as they are, maybe fewer of these fire photos. The cameras don’t usually do so well…

Happy 2014!

### Today’s blog is an excerpt from Craig Packer’s  forthcoming book, “Lions in the Balance: Man-eaters, manes and men with guns”, which will be published by University of Chicago Press in the fall of 2014. ###

When the Italians attempted to conquer Abyssinia in 1887, they provisioned their troops with livestock brought from India, but some of the cattle were infected with the rinderpest virus.  By 1897, the disease had spread south from the Ethiopian plateau to South Africa’s Cape of Good Hope and across to West Africa, killing ninety percent of domestic livestock across the entire continent. Control programs were initiated throughout Africa; by the 1960s rinderpest was restricted to only a few areas, and Serengeti was the last major reservoir in Tanzania.  A cattle-vaccination program around the Serengeti finally eliminated the disease from the wildlife inside the park in 1963.   Liberated from rinderpest, the wildebeest, buffalo, warthog and other ruminant populations grew exponentially until they reached their current plateaus in 1979.

The lion population grew, too, but in a very different pattern.

The lions in the wooded habitat of our study area remained stable from 1966 until 1973 when the population suddenly leapt to a new equilibrium, then remained stable for another ten years before leaping again in 1983.  The ruminant population had nearly tripled between 1966 and 1973; what held back the lions for so long? And what happened in 1973 and 1983?

Our lions endure an annual pattern of feast and famine; the migration brings the wildebeest and zebra within easy reach during the rainier months but sends the herds north to Kenya each dry season.  In normal years, our study lions struggle to persist on warthog and buffalo, but these only sustain the adults – few cubs manage to survive.

The dry season of 1973 was the rainiest in decades, and the unseasonably green grasses attracted the wildebeest and zebra to our woodlands study area more or less continuously until the normal rains returned in November.  Without the usual dry season famine, virtually every cub born in 1973 survived.

These surviving cohorts were large enough to form entirely new prides that could compete successfully against the prevailing social order and redraw the map of lion pride territories.  Tough new gangs squeezed their way into the neighborhood, allowing the lion population to finally rise to a higher post-rinderpest plateau.

The recovering herds not only provided more meat on the hoof, but the wildebeest’s insatiable appetite for grass subsequently modified the habitat in the lions’ favor.  An awful lot of grass was left uneaten when the wildebeest population was held low by rinderpest: grass fires roared through the park each year, burning the young acacia trees to stumps.  But the expanding wildebeest population became the world’s largest lawn service, mowing the grass down to the nubs over thousands of square kilometers – creating fire breaks through much of the park.  By the mid-1970s, less than a quarter of the Serengeti burned each year, and saplings were able to grow unhindered.  Tree recruitment reached a peak in 1980 and persisted for ten years.

Lions need cover to hunt more successfully, and 1983 was the first year with favorable dry-season rainfall in this new improved world for hunting lions.  Once again, the woodland prides recruited large numbers of young – large enough to spawn an expansion of new prides and redraw the map, with more groups packed more tightly than ever before.

The woodlands population crashed during a major disease outbreak in 1994 – lion numbers fell back to levels unseen since the late 1960s.  But in 1999 – the first post-outbreak year with favorable dry season rainfall – the woodland population bounced all the way back up to the same level as in 1983-1993.

On the plains, the population’s initial post-rinderpest spurt occurred sometime after George Schaller’s departure in 1969, reaching a new plateau by 1974 when monitoring of the plains prides resumed.  The plains population remained unchanged until November 1997, when El Niño brought the heaviest rains in forty years.  The grasses on the plains had started growing taller during the early 1990s, and the El Niño floods kept the migration out on the plains for the longest period in decades.  A single year with a more consistent food supply was enough to allow the plains lions to spawn whole new prides in the taller grasses.

As Lenin once said, “Sometimes decades pass and nothing happens; and then sometimes weeks pass and decades happen.”

Thanks to the Snapshot Serengeti camera trap grid, we can now watch the migration respond to year-to-year variations in rainfall.  The next time the lions have a banner year, we will all be able to witness how food on the hoof translates into a baby boom of lucky cubs.