Why Study Elephants Elephants can be found in Africa and Asia. There are two types of African elephants: savanna elephants live in savanna, grassland, and dry woodland habitat, and forest elephants live the dense rainforests of Central and West Africa. Elephants are a keystone species: they exert strong control on community structure and diversity relative to their population size. Keystone species support the healthy functioning of an ecosystem, and their loss can destabilize the entire community. In savannas, elephants maintain open grasslands by knocking down trees to feed on leaves and fruit. Other animals rely on watering holes that elephants dig as a water source in the dry season. Forest elephants knock down trees, creating gaps in the tree canopy that allow other plants to grow, which creates a more diverse forest. Elephants are also important seed dispersers and can disperse seeds up 57 km away from where they were ingested. Elephant poaching and habitat loss have increased dramatically in the past several decades due to human population growth and a rising demand for ivory. These pressures have led to severe declines in elephant numbers and shrinking habitats. Based on the critical role that elephants play in ecosystems, broad efforts are underway to promote conservation of the species and their habitat. The first step of conservation is to assess the current population. In order to best protect elephants, researchers and conservationists are using a variety of methods to survey how many remain, where they live, and how the populations are changing. Background The range of the African elephant is the entire area where the species occurs in the wild. Elephants are known to occupy a wide variety of habitats, from tropical forests to deserts. The International Union for Conservation of Nature (IUCN) gathers and analyzes data on many species including elephants. The IUCN does not carry out surveys – they compile survey data produced by other organizations, assess the quality, and estimate elephant range and numbers based on these data. An elephant's home range is the area that they regularly travel to find food, water, and mates, and can span more than 32,062 km2 . Save the Elephants (STE), a nonprofit organization based in Kenya, has been studying the daily movements of elephants across Africa using Global Positioning System (GPS) collars. One of their study sites is Samburu Reserve in Kenya, shown on the map. These collars provide real-time data on elephant movements, which can be used to map the home ranges of elephants. These data can also provide information on resource use, group interactions, and conflict with humans. Female elephants form stable social groups with other females and their young, so collaring one mature female can provide data on a much larger group. Male elephants are generally solitary or form short-term, variable groups, and so collaring a male elephant may only provide data on one individual. The Great Elephant Census (2014-2016) is the first large-scale aerial survey of elephants across Africa in more than 40 years. It aims to get an accurate count of savanna elephants throughout Africa. The project (founded and managed by philanthropist Paul G. Allen) brings together elephant nonprofit organizations and governmental organizations to conduct 72 aerial surveys in 20 countries using standardized methods. The map shows the surveys that are complete, underway, and planned. Most methods of counting elephants sample the population in order to estimate population size, whereas individual registration is a process that attempts to document every individual in a population. Elephants can be individually identified through unique features such as the size and shape of their tusks, notches and holes in their ears, and markings on their face or body. Dr. Joyce Poole is a co-founder of ElephantVoices, a nonprofit organization engaged in elephant conservation as well as in long-term research on social behavior, communication, and cognition. Poole and her husband, Petter Granli, have registered individual elephants in Amboseli National Park and the Maasai Mara ecosystem in Kenya and in Gorongosa National Park in Mozambique. Methods In 2007, the IUCN published the African Elephant Status Report, which included data on the range and population estimates for elephants across Africa. They gathered data from a variety of organizations that monitor local elephant populations. In order to determine the entire elephant range, they gathered evidence of elephant presence or absence in an area, which includes direct observations and indirect signs such as elephant dung and footprints. For each data source, they classified the range information into one of four categories: ● Known Range – areas where elephant presence has been confirmed within the past 10 years and the habitat is still suitable for elephants. ● Possible Range – areas within the historical elephant range where the habitat is suitable and there is no data to rule out the presence of elephants. This area includes former "known" elephant range where data is more than 10 years old. ● Doubtful Range – areas where there is evidence to suggest that elephants are not present, but no rigorous survey data exist to confirm their absence. If an area is extensively surveyed and the absence of elephants is confirmed, the area is reclassified as "non-range." ● Non-Range – areas where the absence of elephants has been confirmed, either through extensive surveys or habitat modifications that would make the habitat unsuitable for elephants. The map shows the "known" and "possible" range combined of elephants across Africa based on this 2007 study. STE researchers sedate an elephant from a helicopter by firing a syringe using a tranquilizer gun. They attach the GPS collar (weighing 12 kg) around the elephant's neck and wake the elephant by injecting it with an antidote. The GPS collar transmits positional information at a predetermined time interval, which can be received on computers or mobile phones. The location data is accurate to about 5-15 meters, and most collars are set to report every hour. These data are then analyzed using a geographic information system (GIS) to learn about the elephant's home range and movement patterns. The aerial surveys are conducted using a small airplane with four crew members: a pilot, two observers, and one recorder. The observers note the number of elephants, group composition (family or males), GPS coordinates, elephant carcasses, other species, and human disturbances within the counting strips on either side of the plane. Groups of elephants are photographed with cameras mounted on the aircraft to be confirmed later. Within each country, survey areas are divided into regions, called strata, and depending on terrain and vegetation, survey teams use one of three survey methods to obtain elephant counts in these strata: ● Transect sample counts are the preferred survey method, suitable in relatively flat terrain with sparse vegetation. The survey aircraft flies back and forth along parallel transect lines that are about 2.5 km apart and that begin and end at opposite sides of the stratum. Observers count elephants within 150-meter "counting strips" on either side of the plane (see figure). The counting strips are the areas that are being sampled within the stratum. ● Block sample counts are used in hilly terrain where it is difficult to fly straight-line transects across a large area or where vegetation is dense. Small areas, called blocks, are chosen randomly within a stratum. Within each block, the aircraft flies along transects that are sufficiently close to one another to ensure that the counting strips cover the entire block. The blocks are the areas that are being sampled within the stratum. ● Total counts are used where the sampling area and elephant population are small or elephant distribution is highly clumped. The aircraft flies along transects within the stratum that are close enough together to ensure that the counting strips cover the entire stratum. Because researchers survey the entire stratum, this is a total count rather than a sample count. Strip Transect Sampling Method In all survey methods, transects are oriented perpendicular to rivers or other natural features, to reduce the variance in elephant densities between transects. The width of the counting strips must remain consistent, because the width is later used to calculate the proportion of the survey area that was sampled. To achieve consistency, the pilot flies the plane at a constant height of 91.4 meters using a laser altimeter. Visual guides on the wings mark the 150-meter-wide visual search area for the observers. The plane flies at 160 to 180 km/hr covering about 1 to 1.5 km2 per hour. The map shows the survey area for the Zambezi Valley in Zimbabwe, with transect sample counts in strata with flat terrain and block sample counts in strata with hilly terrain. The total count method was not used in this survey area. Individual registration involves identifying each elephant in a population based on its sex, age, and unique features and markings. A set of ID photos is taken of each adult elephant. Ideally, ID photos include the left profile, the right profile, and head-on with the ears extended. In addition, photographs of any other distinguishing marks, such as scar tissue, a damaged trunk, or a satellite collar, are taken. Although a full set of ID photos may also be taken of immature elephants, they are usually identified by sex and age in the context of their mothers. Poole and Granli developed a digital database used to register elephants, which includes the key features that describe an elephant (e.g., estimated age, sex, family membership, left and right tusk configuration, left and right ear notches and tears, ear shape) and up to six ID photos. This information becomes an elephant's digital ID card. To register a new elephant, the scientist must make sure that the elephant isn't already registered in the database. If the elephant is deemed "new," it is registered with a unique number and/or name. Once all individuals in the study area are registered, the total number of elephants registered is the population size. Advantages The IUCN is the only group to date to gather comprehensive information about the entire range of elephants across Africa. This data is unique and valuable for elephant conservation and management efforts. GPS collars allow researchers to track elephants remotely without the need for observers to follow elephants in the field, reducing the effort and cost. Tracking can also occur at night and in forests, where poor visibility would limit human observation. Large amounts of high-quality, detailed spatial data are generated that can easily be visualized on a map and compared to other spatial data, such as rainfall or vegetation patterns. Aerial surveys are the most common method for directly counting large numbers of savanna elephants spread across vast landscapes. Because of their large size, elephants in open habitats are easy to identify from aircrafts or helicopters. Aerial surveys also allow researchers to census areas that are inaccessible on the ground. An aerial survey costs about 25% of what a dung survey covering the same area would cost. The map shows the survey area for the Zambezi Valley in Zimbabwe, with transect sample counts in strata with flat terrain and block sample counts in strata with hilly terrain. The total count method was not used in this survey area. Studying elephants individually over many years offers scientists a wealth of detailed information — beyond a population count — that cannot be captured with other survey methods. Information on location, group size, and behavior that are collected while observing individuals provides insights into social behavior, communication, and ecology. Demographic information allows scientists to know the age structure of the population, interval between calves, and age at first reproduction, data that can be used to model population growth rate. Population trends can then be tied to environmental conditions such as periods of higher or lower rainfall. Disadvantages The time, effort, and authority necessary to collect data on this scale is challenging and is best suited for major, reputable conservation organizations, such as the IUCN. The availability of data on elephants is inconsistent across areas. In some areas, they have been surveyed extensively and with a high degree of confidence, whereas in other areas, no data exists or sources are unreliable. It can also be challenging to determine if elephants are truly absent from an area or present but unobserved, leading to a "false absence" report. The difficulties of observing elephants in some habitats, such as dense forests, can lead to a possible underestimate in elephant range in these areas. Determining precise range boundaries is difficult because the data is less accurate at the edges of the range. Also, some range boundaries may be somewhat arbitrary, as surveys may stop at natural barriers, such as rivers or mountain ranges, or borders of national parks or countries, and this ignores elephant movement across boundaries. Attaching collars to elephants that have been anesthetized is dangerous for both the researchers and the elephants, and must be repeated every 2-4 years to replace the batteries in the collars. The initial costs of the GPS collar and the helicopter capture are high and the process requires highly trained staff, but the subsequent costs of collecting the data are low. Data from collars are sometimes lost during transmission because hilly terrain and dense forests interfere with the signal and data must be curated for errors due to technical issues before final analysis. The primary drawback of individual registration studies is that they are labor-intensive and costly. Dedicated observers must learn to recognize the individuals in the population and monitor life history events on a regular basis. To capture long-term trends in population size and meaningful demographic data requires many years of observation. Individual registration can also become impractical with large populations or those that range over vast ecosystems. Survey Design Survey Design Several methods can be used to survey elephant populations. The appropriate technique for a particular area will depend on the question being asked, the habitat, and resources available to conduct the survey. Each survey method has advantages and disadvantages that researchers must take into account before choosing a method. Animals can be surveyed using direct methods (counting the animals themselves) or indirect methods (counting signs or signals, such as dung, tracks, or sounds). After a method is chosen, the researchers map out the study area, which is the total area they are surveying. If a study area includes several different habitats, such as grassland and forest, or mountains and plains, the study area is divided into strata, or sections, for each habitat. The methods are then adapted to fit the conditions within each stratum. Within each study area or stratum, researchers can choose to perform a total count or a sample count. A total count is when the entire study area is surveyed, while a sample count is when parts of the study area are surveyed and the results from those parts are applied to the entire study area to estimate the total population size. When a sample count is performed, sampling areas can be in the shape of strips, blocks (or polygons), and points. Sampling areas are selected throughout the study area or stratum in either a random or regular fashion. Random sampling is usually preferred because it avoids bias, but in some cases, placing the sampling areas at regular (or equal) intervals is preferred. When sampling in strips, researchers first draw transect lines and the strips are the areas to the right and left of the transect line. Transect lines are typically drawn at regular intervals. Blocks are polygons selected around random points and the entire area within the block is surveyed. A point survey entails stationing an observer, an audio recorder, or a camera at random points in the stratum for a period of time. If researchers are measuring sounds the distance at which sound can be detected around the point determines the area that is being sampled. Aerial surveys are most effective on relatively flat ground with sparse vegetation. They cannot be used to survey forest elephants, which are difficult to see from the air. Aerial surveys require significant resources including an airplane and specialized equipment, as well as a pilot and experienced observers. Sample counts assume that the count performed in the sampling area can be extrapolated to the entire survey area. Nonuniform elephant distributions can lead to undercounting or overcounting, depending on the herd distribution at the time of the survey. Undercounting can also occur when calves hide under an adult's belly or in the center of the herd. Overcounting can occur when elephants that have already been counted move to an uncounted transect and are counted again. Total counts can be more accurate but are too expensive and time-consuming to undertake in a large survey area. Population estimates based on aerial surveys can be imprecise due to variations in the landscape and elephant distribution, and human sampling error. However, researchers can reduce errors by selecting the appropriate type of aerial survey for the landscape and elephant distribution, by keeping flight speed and height consistent, and by double-checking observers' identifications. The map shows the survey area for the Zambezi Valley in Zimbabwe, with transect sample counts in strata with flat terrain and block sample counts in strata with hilly terrain. The total count method was not used in this survey area. Forest elephants are hard to see in dense forests, making aerial survey techniques impossible to use. Although they are hard to see, forest elephants frequently make sounds to communicate, often below the frequency that humans can hear. These low-frequency calls can travel far through forests, particularly the infrasonic frequencies. Researchers from the Elephant Listening Project (ELP) at Cornell University, led by Dr. Peter Wrege, study these calls to estimate forest elephant abundance in the Congo basin of Central Africa, the largest block of tropical rainforest outside of the Amazon. ELP researchers first studied forest elephants in Dzanga National Park in the Central African Republic to determine the calling rate, or the number of calls elephants make in a given time period. They set up six audio recorders around the edge of a forest clearing and observed elephants from a platform, recording the number of elephants visible in the clearing (see figure below). The six audio recorders simultaneously recorded the elephant sounds, and researchers triangulated the location where each call came from to determine whether it came from inside or outside of the clearing. They then matched the data with the number of elephants observed to calculate the calling rate. This allowed the researchers to estimate the number of elephants in any location in a forest elephant habitat, based solely on the number of calls recorded. They also determined that the area in which a single audio recorder can reliably detect elephant calls in this habitat is 3.22 km2, which represented the sampling area around each recorder. The sampling area must be adjusted for each study based on the amount of background noise present in that habitat. The white area is a forest clearing and the gray area is forest. Circles are audio recorders around the clearing, triangles are audio recorders in the forest, and the black rectangle is the viewing platform. Source: Thompson et al., 2009 ELP researchers then conducted a survey in Kakum Conservation Area, Ghana, using the calling rate model they developed in Dzanga National Park to estimate elephant population size in this forest. They set up nine audio recorders at random points within the forest and recorded simultaneously for 38 days (see figure below). They counted the number of elephant calls recorded during 20-minute sampling periods at each location. The sampling periods were 4 hours apart from one another to reduce the chance of counting the same elephants. Based on the higher background noise level at the study site, the sampling area of each recorder was estimated as 1.14 km2. Finally, they multiplied the elephant abundance within the sampling areas by the area not covered by the recorders to get the total estimated elephant population in Kakum Conservation Area. The light gray area is Kakum Conservation Area. The numbered points are the locations of the audio recorders and the dark gray rings around the points are the sampling areas of the recorders. Source: Thompson et al., 2009 Acoustic surveys are effective for surveying forest elephants because they can cover large areas for long periods of time in dense forests that are hard to study otherwise. Acoustic surveys sample a larger area with less effort than a dung survey, the other common technique for surveying forest elephants. A single acoustic sensor can sample an area of about 3 km2 in a quiet forest, while an equivalent-effort dung transect covers only 0.1 km2. The population estimates obtained from acoustic surveys are comparable to those from dung sampling, but their precision is higher, producing confidence intervals half as wide as those from a dung count. Since the data are recorded automatically, human bias is greatly reduced. Acoustic methods also record at night, when it is particularly difficult to gather data on forest elephants. The acoustic recorders also collect data on human activities in the area by recording noises such as chainsaws, gunshots, and vehicles. Since the stations record simultaneously, elephants are not counted twice within the same survey, which can be a problem with other methods such as aerial or ground counts. Acoustic surveys require specialized equipment and training to perform the survey and analyze the results, whereas more common techniques like dung sampling are relatively easy to do and require very basic equipment. With acoustic sampling, researchers can't see the elephants, so they can't record additional information, such as sex, age, group size, and body condition. Background noises, such as thunderstorms, can reduce the ability to detect calls, either because the noise interferes with elephant calls, or because elephants call less frequently during storms. Dung transects are the most common technique for surveying forest elephant populations. The dense forest vegetation makes it difficult to count elephants directly, so an indirect method, such as counting dung, is necessary. Dr. Fiona Maisels of the Wildlife Conservation Society (WCS) has helped to design and implement survey methods for primates and forest elephants. She and her colleagues gathered data from dung transect surveys performed in five countries in central Africa to estimate the changing sizes of the forest elephant population. This method relies on estimating the elephant population size by counting dung piles and knowing how often elephants defecate and how fast dung piles decay. Based on published studies, researchers determined the average rate that elephants defecate: 19.77 dung piles per elephant per day. They gathered information on the time dung takes to decay to the point of disappearance at 14 sites across various habitats and seasons and calculated the average, which was 81.82 days. The survey areas in each of the five countries were divided into strata, and a minimum of 15 transect lines per stratum were regularly placed perpendicular to features such as roads and rivers to avoid sampling bias. Dung transects were performed in one of two ways: the line transect method or the recce method. Line transects – Observers walk along transect lines and measure the perpendicular distance from the transect to the center of each dung pile they observe. Even though the dung piles are distributed over the landscape, they become harder to spot the farther they are from the transect line, decreasing the chance of detection. Modeling software is used to compensate for the missed dung piles and produce a corrected estimate of the total number of dung piles within a maximum distance from the line. Recces – Observers walk along lines and count all dung piles they observe within a 2-meter strip (1 meter on either side of the line). It is assumed that the observers detect all of the dung within the 2-meter strip. When a large enough percentage of the survey area is sampled, dung surveys can be as accurate as other survey methods. They are relatively easy to implement and don't require specialized equipment, but intensive and careful training is required. Elephant dung is easier to detect than the elephants themselves and generates more data than a ground survey of elephants. As dung counts measure dung deposited over time, this method is less sensitive to elephant movement between sampling areas or the clumped distribution of elephants. Dung surveys are extremely time- and labor-intensive, and can be expensive if the survey area is large. This method assumes a stable elephant population creating stable rates of dung accumulation and decay during the study period. Because dung decay times are long, more rapid changes in the elephant population may lead to inaccurate estimates. The rate of dung decay and defecation can also vary with habitat and season. While less clumped than elephants, dung piles are typically not randomly distributed. To avoid inaccurate estimates due to the clumped distribution, the transects need to be arranged throughout all vegetation types in a manner that is representative of the different habitats. It is often advisable to stratify the study area by vegetation type and/or by poaching intensity. A minimum of 30 transects per stratum is advised to improve the precision of estimates. Unselect all layers except the "1979 Range" layer. The map shows the entire elephant range in 1979, at the beginning of the ivory crisis. The total estimated elephant population in 1979 was 1.3 million elephants. Select the “2007 Range” layer to see how almost four decades of habitat loss and illegal poaching for ivory has affected elephant range (savanna and forest elephant combined). It decreased by about half, and due to human land use, much of the remaining habitat is in protected areas. The total estimated elephant population in 2007 was approximately 640,000 elephants. Select the “2016 trends” layer to see trends based on initial data from the Great Elephant Census, a Paul G. Allen project. This layer shows the area that the census covered – about 80% of savanna elephant range. Purple areas are places where elephant populations are stable or growing, while red areas are places where populations are declining. Conservationists can use this information to focus their efforts on protecting elephants that are under threat. Unselect layers as necessary for better viewing of individual layers. The density of elephants within the sampled area can be estimated using the following formula: Elephant Density = (dung density)/(defecation rate x decay time ) The number of elephants in the population was then estimated by modeling. The relationship between elephant density and a number of variables known to affect elephant abundance was calculated using multiple models. The models that best fit the data were chosen, and then, using maps that cover the entire range, the selected models were used to predict elephant density in areas that were not sampled.
