Understanding the Elusive: Conservation in an Rapidly Changing World – PART 2

Deciding which species “deserve” the most resources and attention in terms of conservation can be a contentious issue at the best of times. Members of the general public tend to favour protecting the cute and cuddly however, are these characteristics really the most effective way to decide how to direct our efforts? Using a publication written by Chapple et al. (2011) and estimating white shark populations in California, USA, as a case-study, this two-blog series aims to highlight:

• The difficulties of estimating population sizes of marine species
• The importance of the production of the most accurate information possible from the scientific community, and
• The impact of these factors on the success of conserving endangered marine species.

Case Study: The White Shark in Californian Waters

The white shark (Carcharodon carcharias) represents one of the world’s most popular apex predators. Due to their cosmopolitan distribution, perceived population declines, concerns for the potential for them to become overfished, as well as the vulnerability inferred from white sharks’:

• Long life span (approximately 30 years)
• Late arrival at sexual maturity (10-15 years)
• Production of between 2 to 10 pups biannually (gestation period of 12-18 months)

White sharks have been protected under legislation and/or fisheries restrictions in the following countries for numerous years:

• South Africa (1991)
• Namibia (1993)
• Australia (1999)
• Malta (2000)
• Mexico (2002)
• New Zealand (2007)
• United States:

• California (1994)
• North-west Atlantic and Gulf of Mexico (1997)
• Remainder of the US Exclusive Economic Zone (EEZ; 2005)

The highly migratory nature of these sharks however, makes it highly probable that these animals will travel outside of protected waters where there is potential for them to fall victim to oceanic and coastal fisheries. As a result of this, white sharks are also currently listed through:

• The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)
• The Convention on Migratory Species (CMS)
• The International Union for Conservation of Nature
• Lists white sharks as vulnerable

The naturally low numbers of these sharks in an area at any one point in time, alongside their migratory nature, makes accurately estimating their population sizes difficult to achieve and so researchers tend to focus on areas they are known to aggregate. A study by Chapple et al. (2011) did just this, focussing on the areas around the Farallon Islands and Tomales Point to estimate the population size of white sharks off of the central California coast in the USA.

As discussed in my previous blog, Chapple et al. proposed that the central California population of white sharks consists of only 219 mature and sub-adult individuals. This low estimate created serious – and legitimate - concerns about the status of white shark populations in Californian waters, prompting petitions to have the species put on the endangered species lists for the State of California.

What’s the big deal about listing a species as endangered?

The listing of species on endangered lists can be viewed as major achievement by conservation organisations and as a result of this, listing decisions can often be rushed before the published population estimates have a chance to undergo even a minimum level of critical scientific review. Not only do these decisions place substantial demands on governments to devote considerable resources to protecting the animal in question, but they also impact groups within the general public who must forgo social and economic opportunities to ensure that they do not break the protective laws. Most importantly, listing species that are not under true threat of biological extinction will divert resources away from those which are genuinely at risk of meeting this fate; defeating the purpose of implementing these conservation and management policies in the first place.

So, what about the results of Chapple et al.’s study?

If correct, the low estimates of white sharks presented by Chapple et al. justifiably raise concerns for the status of the white shark population in California and the ENP. A recent re-evaluation of the size of the white shark population off the Californian coast conducted by Burgess et al. (2014) however, has since indicated a minimum all-life stages population size of over 2,000; suggesting that the population of white sharks in this area is at least stable.

What does this mean for white sharks in California? Should they still be protected?

In the last two decades, global shark numbers have been in rapid decline due to increased human pressures in the form of long-lines, targeted fisheries, and shark fining practises with populations decreasing by 70% worldwide. The white shark is not immune to these global threats and due to their unfortunate involvement in numerous fatal shark attacks across the past 3-5 years they face the added pressure of being the targeted by multiple drum-line and shark net programs across the globe. Burgess et al.’s newest population estimate and recent observations indicate that the existing conservation and management measures in Californian waters for white sharks are sufficient and their population is likely to be improving. Although this places doubt on whether the white shark should be listed as endangered in this area, it does not mean that the protection of these animals should be stopped. As well as maintaining current protective measures, the status of these animals should be regularly monitored using a variety of techniques to avoid unbiased results.

The results of Burgess et al.’s review also highlight the need for multiple modelling approaches to be used when assessing the population dynamics of such a migratory marine species. Researches should be motivated to undertake a more complete analysis when considering white shark populations to ensure that the most accurate information possible, with full disclosure of uncertainties and potential errors, is available to the public at all times. Aiming to produce the most accurate population estimates possible will ensure that the limited resources available for conservation efforts is not misdirected and that protective measures will be applied to the species which need them most.

Conservation efforts must remain dynamic and flexible to reflect the rapidly changing environment and animal populations around us, especially in a time where the budget for such efforts is minimal. The review of Chapple et al.’s study by Burgess and his colleagues should not be viewed as a corrected mistake, but a step in the right direction and further development of our understanding of these elusive animals. We should always strive to learn more and protect what we have, while we still have it.

Lauren Peel

Oceans Research P.I. and Field Specialist

References

Burgess GH, Bruce BD, Cailliet GM, Goldman KJ, Grubbs RD, Lowe CG, Macneil MA, Mollet HF, Weng KC, O’Sullivan JB (2014) A Re-evaluation of the Size of the White Shark (Carcharodon carcharias) Population off California, USA. PLoS ONE 9(6): e98078.

Chapple TK, Jorgensen SJ, Anderson SD, Kanive PE, Klimley AP, et al.. (2011) A first estimate of white shark, Carcharodon carcharias, abundance off central California. Biol Lett 7: 584-583.

Understanding the Elusive: Conservation in an Rapidly Changing World – PART 1

Deciding which species “deserve” the most resources and attention in terms of conservation can be a contentious issue at the best of times. Members of the general public tend to favour protecting the cute and cuddly however, are these characteristics really the most effective way to decide how to direct our efforts? Using a publication written by Chapple et al. (2011) and estimating white shark populations in California, USA, as a case-study, this two-blog series aims to highlight:

• The difficulties of estimating population sizes of marine species
• The importance of the production of the most accurate information possible from the scientific community, and
• The impact of these factors on the success of conserving endangered marine species.

The Challenges of Modelling the Population Size of Migratory Marine Species

In 2011, a study completed and published by Chapple et al. estimated that the central California population of white sharks consisted of only 219 mature and sub-adult individuals. Their study was conducted over a three year period in two focal areas (both of which are well-established seal rookeries) around the Farallon Islands and Tomales Point in which white sharks are known to aggregate. As the dorsal fin is the equivalent to a ‘fingerprint’ for individual white sharks, photographs of dorsal fins were used by Chapple et al. to generate abundance data of the number of individual white sharks seen across these two sites throughout the study period. Population estimates were then subsequently modelled for sharks in this area.

In order to model these population estimates, Chapple et al. made five key assumptions:

1. Their study white shark population was closed
2. There was homogenous sampling of animals and all individuals had an equal probability of capture
3. The “tagging” process did not influence the chance of recapture
4. There was zero “tag” loss
5. Photo-identifications of white sharks at these two aggregation sites represented a random sample of the central California population

If correct, the low estimates of white sharks presented by Chapple et al. justifiably raised concerns for the status of the white shark population in California and the ENP. Just as with any scientific publication however,

“it is important to consider the potential for methodological flaws and assumption biases that may have resulted in an under-estimation of the actual population size” (Burgess et al., 2014)

In June of 2014, George Burgess and his colleagues published the results of an important re-evaluation of the size of the white shark population off of California, USA, based upon a data set collected at the same sampling locations as Chapple et al.’s 2011 study (Jorgensn et al., 2010). The differences in the estimates of the white shark population size off of California between the two studies was staggering, with Burgess et al.’s estimate (2014) indicating a minimum all-life stages population size of over 2000 individuals.

Burgess and his colleagues found that all five key assumptions made by Chapple et al. (2011) had been violated, resulting in an underestimation of the white shark population in this area.

Assumption #1: Closed population 

By assuming that the study population was closed, Chapple et al. effectively assumed that all mature and sub-adult white sharks would return annually to the seal rookeries of their study. However, considering that:

• Multiple examples in the literature have shown that most sharks do not return annually to particular aggregation sites
• Some sharks within the ENP may be located within the region but not in either of the two study areas and therefore will not be accounted for in the study
• The number of unique individuals identified by Chapple et al. increased each year (suggesting an immigration of sharks during the study)

It was concluded by Burgess et al. that both the existing literature and Chapple et al.’s own data demonstrated that the study population was in fact open over the three years of data collection; thus violating a key model assumption.

Assumption #2: Homogenous Sampling of Individuals

In more layman’s terms, Chapple et al. assumed that every shark had an equal chance of being sighted, and that sharks at the two aggregation sites which they collected data mix in a homogenous or “equal” manner with each other.

Although it is well known that white sharks do show site fidelity to seal aggregation sites or rookeries, research has also shown that individual sharks show preference to specific locations and may restrict their movements as a result of this; limiting the mixing of individuals over small spatial distances. Based on these findings alone, it is clear that Chapple et al. should not have assumed homogenous sampling as they in fact had an increased probability of re-sampling previously observed sharks at each of their sample sites. This assumption violation results in a low bias towards their population estimates.

Assumption #3: Tagging method does not affect subsequent chance of sampling

One of the main issues with using photo-identification to model white shark populations is that it requires the sharks to be lured and baited to the surface where they can be photographed. It is therefore assumed that all sharks have an equal probability of being attracted, and that all sharks in the area will have an equal chance of being attracted again. However:

• In comparison to acoustic detections done by the Oceans Research team in Mossel Bay, photo-identification has been found to show the lowest probability of detection and tended to underestimate residency times and local abundance for white harks
• Intra-specific dominance patterns between large and small sharks may exclude some individuals from the area or inhibit their approach to the surface, leading to greater probability of low quality dorsal fin photographs and under-reporting of shark numbers
• Some individuals may learn that the bait does not lead to a food reward through negative attraction conditioning. These “trap-shy” sharks will therefore have a smaller probability of attraction during subsequent sampling events and be less likely to be re-sighted.

Although being unable to re-sight previously ‘tagged’ sharks may lead to population over-estimations, the latter two factors combined would lead to an underestimation of white shark population size, which is what Burgess et al. believes to be the case in Chapple et al.’s study.

Assumption #4: Zero tag loss

Unlike a fingerprint, the primary characteristic markings on the dorsal fin of white sharks – the pattern of notches on the trailing edge of the fin – have the potential to change with time. Although this “tag-loss” as a result of marking changes does not necessarily result in over-estimation of population size, it introduces the probability that individuals can be present but not correctly identified; violating the fourth assumption made by Chapple et al. (2011).

Assumption #5: Random sampling of the central California sub-population using photo identification

Burgess et al. commented in their review of Chapple et al.’s study that this was the most serious of all assumptions violated by the research group. As white sharks in the Californian region have been observed to reside predominantly at a single aggregation site and less often at others, the sharks sampled by Chapple et al. cannot and do not represent random samples of the central California white shark population. Instead, sampled sharks represent only sharks that visit these two aggregation sites either a single time or consistently over the study period. This violation is further compounded by the lack of sampling elsewhere in this oceanic region, such as the known white shark aggregation site of Año Nuevo Island which was excluded from population modelling for ‘logistical reasons’.

This post highlights how difficult it can be to not only collect abundance data for marine species such as white sharks but also how difficult accurately modelling and monitoring their population sizes can be. As Burges suggested models cannot be applied blindly, but careful consideration of the assumptions behind is urged.

But what does this all mean in terms of conserving the white shark and other marine species? Does it really matter if the numbers aren’t quite right?

Keep posted for my next blog outlining the issues of protecting, conserving and monitoring marine species and why it is important that the community is supplied with the most accurate information possible in regards to population sizes and dynamics.

Lauren Peel

Oceans Research P.I. and Field Specialist

References

Burgess GH, Bruce BD, Cailliet GM, Goldman KJ, Grubbs RD, Lowe CG, Macneil MA, Mollet HF, Weng KC, O’Sullivan JB (2014) A Re-evaluation of the Size of the White Shark (Carcharodon carcharias) Population off California, USA. PLoS ONE 9(6): e98078.

Chapple TK, Jorgensen SJ, Anderson SD, Kanive PE, Klimley AP, et al. (2011) A first estimate of white shark, Carcharodon carcharias, abundance off central California. Biol Lett 7: 584-583.

Jorgensen SJ, Reeb CA, Chapple TK, Anderson S, Perle C, et al.. (2010) Philopatry and migration of Pacific white sharks. Proc Roy Soc B 277: 679-688.

Delaney DG, Johnson R, Bester MN and Gennari E (2012) Accuracy of using visual identification of white sharks to estimate residency patterns. PLoS ONE 7(4): e34753. doi:10.1371/journal.pone.0034753

To fence or not to fence, that is the question!

Conservation is the responsibility of the state, but Africa is a poor continent, and as a consequence conservation in Africa has unique challenges, as Governments can’t fulfill the role of funding the conservation efforts. National parks and reserves have to find a way to get an income to support their conservation efforts.

Tourism has the potential of creating funds, but not enough to cover all expenses. Non-governmental organizations such as WWF, IFAW and CI to name a few contribute immensely to the conservation effort, but still more funds are needed, which bring me to the controversial topic of utilization of natural resources by the local populations around conservation areas.

I am going to use a few examples I have encountered over the last couple of years, working in southern Africa.  South Africa is the only country where National Parks are totally fenced and this is in the process of changing, with the establishment of Trans Frontier Parks. The fence between Limpopo National Park in Mozambique and Kruger National Park was removed a few years ago to use an example. Fencing is an agricultural practice and once a Reserve or National Park is fenced, we have to manage it more intensely as we have curbed certain natural processes. Numbers of game can increase to numbers higher as the carrying capacity of the area. In times of drought water and food supplements has to be supplied as natural migration routes was blocked. This can have a negative impact on the vegetation, and to keep damage to the vegetation to a minimum we must start inhumane practices such as culling to control game numbers.

So what is the alternative? Will it be possible for humans and wildlife to coexist and to utilise the same resources? Prior to the arrival of Europeans on the Dark Continent this was the practice and did humans and wildlife indeed coexist. But we don’t live in Utopia anymore and alternative strategies are needed. 

Here are a few possible alternatives.  Kafue National Park in Zambia, 22 400 km² the second largest park in Africa is unfenced. Around the park is a buffer zone of 10 to 15 km wide where utilisation of resources are allowed by the local population. Hunting concessions are sold to professional hunting operators by ZAWA and the income created is used for conservation and for creating an infrastructure in the local population adjacent to the park. All meat from hunting goes to the local population, as well as some of the hunting fees. Tourist operators build lodges in the buffer zone which create jobs for the locals, as well as chances to sell curios and fresh produce to tourists and lodges.

Botswana, where wildlife and humans coexist to a certain extent.  Along the western side of the pan handle just above the Okavango Delta, humans and elephants coexist. Humans farm along the river and go through their daily tasks during the daylight hours and once the sun sets spend the evenings indoors. The elephants on the other hand spend their days, 20 – 30 km north of the river, and once the sun sets move down to the river and spend their evenings on the banks, drinking and foraging. They leave before sunset and move back along corridors between homesteads. There are some crop raids, but other methods to keep elephants out of fields such as chilly plant hedges around crop fields and the burning of chilly balls, (a mixture of elephant dung and chilly plants) are used.

 

So is there still space for fences in conservation?A recent publication in Biological Conservation: 176 (2014) 162-171, Fencing protected areas: A long-term assessment of the effects of reserve establishment and fencing on African mammalian diversity by Massey et al., in Aberdare National Park in Kenya. This study used long term data sets at two sites in the park collected over approximately 50 years. The two sites, Tree Tops on the perimeter, and The Ark away from the perimeter of the park. The park was partially fenced in 1991 enclosing the two study sites.They looked on the effect the fence had on wildlife populations. Their findings are very interesting, initially the fence had a positive effect on wildlife, and game numbers increased at Treetops. Although there was fluctuations on species richness at both sites, the Ark was much more stable during the study. Comparing the total mammalian biomass at both sites, the same pattern was seen, a decline at Treetops and stability at The Ark. The fence created an edge effect that had a negative impact on game numbers, species richness, on the other hand, at the Ark, away from the fence it was stable throughout the study. The fence initially kept the impact inside the park to a minimum, and hence game numbers increased, but due to a lack of maintenance and illegal entrance,the local human population encroached into the protected area.This led to illegal practices such as logging, the making of charcoal, and cattle grazing which had a negative impact on game numbers and species richness, proof that a fence is only successful in protecting wildlife if managed properly.

Private Game Reserves with potentially dangerous animals such as lion and elephant in highly populated regions that are focused on the tourist market, must obviously be fenced. This is to keep the danger away from the local population and to protect the livestock of their neighbors. After all small reserves are managed intensely, and can be treated as an“agricultural” practice in the region, with fence maintenance as a priority.

 

Another method might be to fence in the people in and to give wildlife the freedom of movement. The farmers at Panamatenga just south of Chobe National Park have done that. The whole farming area is fenced in with an electric fence and the wildlife can move around the farmland. Ask anybody who have ever been to Kasane in northern Botswana, and they will tell you, the elephants move through town at night, this is a prime example that humans and wildlife can coexist, we just have to adapt our behaviour slightly. After all it is just good manners to be considerate to your neighbors habits and needs.

To conclude, fences have a role to play in conservation. In areas of conflict between wildlife and humans, fences can form a barrier protecting humans from potential danger and at the same time protect conservation areas from human impact.

Let us rather try to find ways to move away from fencing,especially in larger reserves and National parks,  fences are expensive and difficult to maintain,  and sometimes not successful in protecting wildlife and humans alike. Mozambicans are allowed to stay within the boundaries of their  National Parks and Reserves, maybe that is something to look at, as long as there is not an over utilisation of resources, we can all live in harmony, maybe Utopia once again!

Jo Fourie

Oceans Research

Wildlife Research Unit

Wildlife Research Unit - a lifestyle

Imagine a typical day in the life of a Wildlife Research Intern at Ocean’s Campus...

Before 8:30am, you have already scarfed down breakfast and are finishing off the last bit of toast in the passenger seat bound for Gondwana Nature Reserve. Reference book in hand, you spot Orange-breasted Sunbirds and yellow Cape Sugarbrids in the entrance to the 14,000 hectacre park. Cheetahs are the target animal for the morning however. You assist expert ranger Jo Fourie in triangulating the exact location of two collared bachelors not far from the visitors’ lodge. This requires tracking by foot and wheel as you make your way through savanna grasslands and up fynbos knolls. Inspect some scat, study a faint print in the track (rhino, you deduce), scout the raptors trolling the plains, then makeshift a pond-side camp for a lunch of your own. The afternoon consists of another game drive, this time to record the behaviors of giraffes within a predator reserve. Rays of sunshine filter through the window; you can feel them bathing down your neck and arms as you follow the patterned long necks with your binoculars. On the short ride back to campus, you chat with Jo about the day’s data, but also about the wonders of ecology, the folktales of animal behavior, and the finer details of life. Another day, another adventure. One thing is certain: Tomorrow will be entirely different.

The Wildlife Research program debuted in May, 2014 as an addition to the suite of eight other educational internships offered by Oceans Campus, in Mosssel Bay, South Africa. It sets itself apart as the only program dedicated solely to developing the skills necessary for running a terrestrial research project. Interns learn various scientific methods for compiling and analyzing professional level research on wildlife species. Projects may involve birds, insects, small animals, and/or large animals like caracals, rhinos, and elephants.

Two years in the making, the program kicked off this month with a bang. First-time intern, Alex Raposo, spent a full week camping in the African bush with senior instructor Arno Smit. There, she learned the technical as well as survival skills that would help her understand the bio-diverse environment on a profound level. When she wasn’t around the fire or procuring dinner, she was tracking animals, learning to identify their footprints by size, shape, and impact. She also studied various scat samples, practiced how to best approach animals, and even got a tutorial on how to properly defend herself in an adverse wildlife encounter.

“I recommend it to anyone who plans to spend a significant time in the bush,” said Alex. “And it was just fun too.”

One highlight for Alex was witnessing the release of a male rhino into the park. It was the second day of her program. Alex watched from a safe distance as rangers assisted the large bull into its new home. The excitement was high for the rhino reintroduction, but also cautious, for rhinos are a controversial issue in South Africa due to rampant poaching. Alex was happy to report that the male rhino had been spotted mating with a young female less than a week into his transition. Perhaps this means the 2015 interns will even get to glimpse a rhino calf.

No day is quite the same for Alex, but each day builds on the last. She has become an expert for example, in the telemetry used to map the approximate locations of collared animals, especially cheetah and rhino. She has also assisted the senior instructors in collecting data for a project on giraffe behaviors. The hypothesis revolves around whether the giraffes in Gondwana, where predatory lions share the same park, act differently than giraffes in predator free parks. Other projects include trapping small mammals to study genetic diversity and survival rates, camera trapping for nocturnal activity, and crunching bird data to research whether or not there exists a difference in diversity between nature reserves and local farms.

By the end of her time in Gondwana, Alex will have composed a research proposal of her own design. She plans to return to the University of Toronto where she will be a senior this year in order to complete her degree in Biodiversity and Conservation Biology.

Meanwhile, Arno and Jo will be busy going “bush” with a host of new Wildlife Research interns over the next couple month (three for June and six for July). They will continue research started with Alex and begin new projects as they arise. With the start of winter bloom budding the beauty of fuzzy Pretoria and lavender hued Ericas across the Western Cape, it is a promising time for Wildlife Research interns wanting to do some blossoming of their own through a bit of adventure, a lot of learning, and more than touch of fun. 

Jordie Ricigliano