A member of the order Carnivora, Giant Pandas have evolved to specialize on a diet of bamboo (Schaller et al. 1985). Bamboo is a poor food source, low in protein and high in lignin and cellulose, and wild Giant Pandas can only digest an average of 17% of dry matter and about 27% of hemi-cellulose (Dierenfeld et al. 1982, Schaller et al. 1985). Thus, to meet their daily energy requirement, Giant Pandas must consume a large amount of bamboo, up to 12.5 kg per day, and defecate more than 100 times daily (Schaller et al. 1985). Pandas have large, muscular jaws with skeletal features to accommodate the musculature and its famous “pseudothumb” used to hold and manipulate bamboo for processing. However, compared with other herbivores, the Panda has very low digestive efficiency because its digestive tract still resembles that of its carnivorous ancestors. The Panda’s feeding strategy emphasizes volume, requiring it to allocate much of its time to foraging (approximately 14 hours daily).

While morphological and behavioural adaptations provide some compensation for poor digestive efficiency, the Panda’s ability to survive on such a low-quality food source remained mysterious for decades. Even whole-genome sequencing found no specific genes responsible for the digestion of cellulose and hemi-cellulose (Li et al. 2010). An explanation was uncovered in a recent metagenomics study that found the Panda’s gut microbes play an important role in digesting bamboo fibers (Zhu et al. 2011a). Additional adaptations to poor quality diet are found in the Panda’s extreme strategy of energy conservation, with daily energy expenditure comparable to that of a sloth or reptile (Nie et al. 2015). Pandas demonstrate a suite of adaptations to reduce energy expenditure. The thick pelage conserves energy lost through body heat, and it has long been known that pandas are conservative in movement and physical activity. Smaller than expected organs also are indicative of energy-conservation adaptation, and down-regulation of resting metabolic rate has been achieved through a mutation in the synthesis pathway for thyroid hormones.

Giant Pandas also compensate for digestive inefficiency by selecting the most nutritious parts of bamboo plants and by altering diet selection seasonally commensurate with changes in nutritional profiles of bamboo species (Schaller et al. 1985, Pan et al. 2014, Wei et al. 1999, Nie et al. 2014, Wei et al. 2015b). They demonstrate strong preference for seasonally available new bamboo shoots, rich in nutrition and energy and low in fibre. Outside the late spring bamboo shoot season, Pandas favour leaves, although more stems are incorporated into their diet during the winter months when leaf quality and quantity diminishes. This convergence of foraging strategies across variations in climate, bamboo species, and topographic profile indicates an adaptive strategy that serves the species well. Still, as an energy-limited species that spends more than 50% of its time foraging, Panda numbers may be limited by the availability of high quality bamboo and the time required to process bamboo in the digestive system.

Early coarse-scale radio tracking using VHF transmitters provided foundational data on home range size and documented the solitary nature of the Panda’s existence (Schaller et al. 1985, Yong et al. 1994, Pan et al. 2014). Although Panda home ranges overlap generously, direct encounters between individuals are rare. Seasonal elevational migration has been documented in the Qionglai (Schaller et al. 1985) and Qinling mountains (Yong et al. 1994, Liu et al. 2002, Pan et al. 2014). At both sites, the seasonal movements track changes in resources, providing access to bamboo species that provide greater nutritional value. Research integrating behavioural, nutritional, and movement data provide new insights into these seasonal migration patterns, demonstrating that these movements facilitate consumption of higher concentrations and/or a more balanced intake of key nutrients such as Nitrogen (N), Phosphorus (P), and Calcium (Ca) (Nie et al. 2014). Female-biased dispersal has been demonstrated with genetic data in the Minshan and Liangshan Mountains (Zhan et al. 2007, Hu et al. 2010).

Fine-scale documentation of |Panda movement behaviour had to await the advent of Global Positioning System (GPS) technology. Published accounts using high-resolution GPS telemetry revised and added to previous findings (Zhang et al. 2014, Hull et al. 2015). VHF-based radio tracking inevitably leads to large amounts of missing data when animals at more distant locations are not detected, thus it is unsurprising that GPS tracking substantively revised home range size upwards, and that core area overlap and opportunity for social interactions is now understood to be greater than previously believed. Other interesting phenomena were also detected, such as the documentation of female-biased dispersal (confirmed with genetic data; Zhan et al. 2007), and sudden, large movements that temporarily took a female far outside of her home range during the mating season. Fine-scale movement data showed that Pandas exhibited individualistic and multiphasic movement paths within seasonal core habitats and large-scale movements between habitats. Tortuous movement paths indicated when pandas searched for and found foraging resources. Pandas frequently return to the same foraging patches, indicating that they likely have well-developed spatial memory.

Using various measures of habitat suitability, efforts to map Panda habitat have proven valuable for guiding the establishment of the Panda reserve system (Shen et al. 2008, Feng et al. 2009, Qi et al. 2012). Giant Pandas typically occupy temperate montane forests at altitudes of 1,500–3,000 m (Hu and Wei 2004). Range-wide analysis of ecological covariates associated with Panda presence suggested that Giant Pandas are associated with old growth forests, a finding previously unrecognised in studies implemented on smaller spatial scales (Zhang et al. 2011). As an obligate bamboo specialist, the Giant Panda’s reliance on this resource is clear, yet it has usually been ignored in habitat suitability models because mapping bamboo understory using remote sensing techniques is difficult (Linderman et al. 2005). Including understory bamboo in habitat models dramatically decreases estimates of available habitat and increases measures of fragmentation. Advances in remote sensing techniques, such as Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Moderate Resolution Imaging Spectroradiometer (MODIS), Normalized Difference Vegetation Index (NDVI) and Wide Dynamic Range Vegetation Index (WDRVI), combined with new analytical techniques, such as artificial neural network analysis, have helped remove obstacles to including bamboo understory in maps of habitat suitability (Wang et al. 2009; Viña et al. 2008, 2010). Enhanced understanding of Panda habitat requirements and improvements in mapping technologies provide managers and policy makers with better tools for conservation decision-making (Loucks et al. 2003, Xu et al. 2006, Swaisgood et al. 2011, Qi et al. 2012).

Giant Pandas are a solitary and seasonal-breeding mammal, only coming together during the breeding season, from March to May, for reproductive purposes (Schaller et al. 1985, Pan et al. 2014, Nie et al. 2012b). Male Pandas occupy large home ranges overlapping several females and are known to congregate around oestrous females. Male Pandas are able to locate females across large areas, and demonstrate fierce and injurious aggression in competition for access to females. Early in these encounters escalated aggression is common, but, in a possible strategy to conserve energy and minimize risk of injury, once dominance is established, contact aggression is largely replaced with non-contact aggression. Individual males are able to locate and mate with multiple females sequentially, so the mating system might be considered scramble competition polygyny.

Because Pandas live a solitary existence, they must rely heavily on chemosignals to communicate with one another without necessitating face-to-face encounters. Giant Pandas make use of a system of traditional communal scent mark stations that provide them with reliable locations they can visit to deposit signals and investigate signals left by other Pandas (Schaller et al. 1985). Studies documenting habitat characteristics of preferred marking sites, including tree species and microhabitat (Nie et al. 2012a), extend our understanding of habitat requirements for the species. If habitat that promotes communication is not maintained, then poor communication may hinder breeding in the wild, as has been shown for captive Pandas (Swaisgood et al. 2004).

Denning ecology is an important field of study among ursids, and other species giving birth in dens, because access to adequate dens can be important for offspring survival. Forest management practices that affect the availability of suitable dens can either significantly harm or enhance cub survival (White et al. 2001). Ursid young, being extremely altricial, are particularly vulnerable. The Giant Panda lies at the extreme end of this continuum, with the mother weighing nearly 1,000 times the cub’s weight at birth (Gittleman 1994). Den quality may therefore be critical for Pandas. Giant Pandas do not hibernate, but females use rock caves or tree cavities to rear offspring that are produced every 2–3 years (Schaller et al. 1985, Pan et al. 2014, Zhu et al. 2001). Preferred dens are characterized by a small opening to buffer against the elements and provide a warmer and drier environment for rearing offspring (Zhang et al. 2007). Dens tend to be located close to water, presumably so the mother can leave the vulnerable cub (almost always a single cub) unattended for a shorter period of time while she drinks. It has also been proposed that tree dens, once more numerous in primary forests before logging converted many forests in Panda habitat to second growth, are a limiting resource for Giant Pandas (Zhang et al. 2011). The importance of this resource may explain why national survey data indicate that pandas are more often found in primary than secondary forest.

It was once believed, and sometimes still mis-stated, that Pandas’ biological deficiencies were responsible for their own decline. Because of early problems with captive breeding, Pandas gained a reputation for having notoriously low levels of interest in mating; however, Pandas in the wild experience no mating problems and have high reproductive rates (Wei and Hu 1994, Pan et al. 2014). Once a better understanding of the biology and behaviour of the species was incorporated into husbandry practices, captive Pandas began to mate naturally and experienced exponential population growth (Swaisgood et al. 2006, Zhang and Wei 2006, Martin-Wintle et al. 2016). Moreover, its well-known specialization on bamboo is not (as once thought) an evolutionary cul de sac, as it opens up a foraging niche with plentiful resources and few competitors (Wei et al. 2014). Dietary specialization is often seen as an extinction risk factor, but this may not be the case for the Panda, which specializes on widespread and abundant bamboo. Thus, pandas are well-adapted to their environment and have reproductive rates sufficiently high to explain the recovery of populations once bans on poaching and habitat restoration efforts commenced (Wei et al. 2014).

Once widespread throughout southern China, and as far north as Beijing and south into Southeast Asia, the Panda’s distribution is now confined to its previous western extremity in Sichuan, Shaanxi and Gansu provinces. Pleistocene range shifts were associated with the disappearance of the Panda’s principal source of food, bamboo, due to warming climate; whereas rapid range contraction in the past several hundred years is attributed to the conversion of bamboo forests to agricultural cultivation and rapid expansion of human populations (Li et al. 2015). The largest populations are currently found in the Minshan, Qinling, Qionglai mountain ranges, and smaller, more isolated populations remain in the Liangshan, Daxiangling, and Xiaoxiangling mountain ranges (State Forestry Administration 2015).

The Giant Panda’s range is highly fragmented, resulting from centuries of human encroachment and loss of forested habitat at lower elevations. Rapidly expanding industrialization, beginning in the early 1900s and accelerating since 1949, is associated with severe contraction of the Panda’s range (Zhu et al. 2013, Li et al. 2015). While they once occupied forests below 1,000 m in elevation, current populations are restricted to mountain ranges, separated by valleys and flatter landscapes that have been altered by human activities. China lost more than 30% of its forests between 1950 and 2004, coinciding with a precipitous drop in Panda populations, but forest cover has increased in the past two decades (FAO 2010).

The Giant Panda has been the focus of none of the most intensive, high profile efforts to recover an endangered species. In 1981, China joined the Convention on the International Trade in Endangered Species (CITES), which made trade of Panda skins illegal. Enactment of the 1988 Wildlife Protection Law banned poaching and conferred protected status to the Giant Panda (listed as Category I, the highest level of protection). The National Conservation Project for the Giant Panda and its Habitat of 1992 laid out a masterplan for Panda conservation and established a Panda reserve system, which today has grown to 67 reserves. Enlarged by more than 50% since the Third National Survey, this reserve system currently protects 67% of the Panda population and nearly 1.4 million hectares of Panda habitat (State Forestry Administration 2015). The biological diversity of these reserves is unparalleled in the temperate world and rivals that of tropical ecosystems (Mackinnon 2008), thus making the Panda an excellent example of an umbrella species conferring protection on many other sympatric species (Noss 1990).

These efforts to end poaching and protect Panda habitat played a significant role in Panda recovery. The Chinese government also invested in infrastructure and capacity building for reserve staff, established anti-poaching patrol, curtailed human activities inside reserves, and in some cases relocated human settlements from inside to outside of reserves. Other measures directed at broader conservation problems also benefited the Panda. The Natural Forest Conservation Program was implemented in 1997 to reduce the devastating impacts of flooding on human communities due to deforestation and erosion. The program banned logging in most forests in Panda habitat, slowing habitat degradation. Additionally, the Grain-to-Green Program incentivized farmers to plant trees on steep slopes to slow erosion. The result of these policies was the addition of 3 million hectares of forest cover in China annually, an increase of 1.6% per year from 2000 to 2010 (FAO 2010). As a consequence, Panda habitat is recovering and the total occupied habitat has increased by 11.8% between the Third and the Fourth National Surveys; an additional 6.3% increase in suitable but unoccupied habitat was also observed. In the Wolong Nature Reserve, implementation of the Grain-to-Green Program brought about measurable increases in connectivity of Panda habitat (Viña et al. 2007). Thus, these habitat conservation policies are associated with increasing Panda population size, increasing range, and better habitat connectivity. Efforts have also commenced to restore habitat corridors (Wang et al. 2014, Wei et al. 2015a) and to reintroduce captive-born pandas to increase genetic diversity in small, isolated populations.

Ecocompensation has been proposed as an important component of a conservation strategy for pandas (Yang et al. 2013, 2015; Liu et al. 2008, 2015; Tuanmu et al. 2015). Approximately 15% of the remaining unprotected habitat occurs in collectively-owned forests. Payment for ecosystem services, which has already been shown to benefit Panda conservation under the Grain-to-Green Program, could extend conservation measures into these unprotected areas.

Finally, the Giant Panda has been the beneficiary of a massive scientific effort conducted in partnerships between the Chinese government and institutions and international conservation NGOs and zoos (Swaisgood et al. 2010, Wei et al. 2015a, State Forestry Administration 2015). Once poorly understood, there has been an explosion of scientific studies across many disciplines, and this knowledge has increasingly been applied management and policy decisions. Future directions would benefit from even better coordination between science and policy, and the application of adaptive management principles in which experiments are conducted to evaluate management actions that may increase carrying capacity inside protected areas (Swaisgood et al. 2011, Wei et al. 2015a).

China's State Forestry Administration, while rightfully proud of its accomplishments, fully realizes that more work needs to be done to further Panda conservation and to avoid losing ground so painstakingly gained. They plant to continue investing in habitat protection, population monitoring, and protection patrols, and to further develop capacity of reserve staff (State Forestry Administration 2015). They recognize the challenges the future holds, and in particular will seek to address problems of habitat connectivity and population fragmentation.