Chemical Composition of Lick Soils and Functions of Soil Ingested by Common Warthogs ( Phacochoerus africanus ) in Dabena Valley Forest, Western Ethiopia

: To identify chemical composition of lick soil and function of soil ingested by common warthogs ( Phacochoerus africanus ), the study was conducted in Gassi Controlled Area (GCHA); southwestern and in Haro Aba Diko Controlled Hunting Area (HADCHA) northeastern Dabena Valley Forest from May 2016 to June 2018. Top soil samples licked by common warthog were taken from 2.5 cm diameter, 20 cm deep soil cores, from five evenly spaced locations around the periphery of the central 60x60 m grid in each feeding plot. Soil samples were dried under shade for one week and then kept at 28°C until analyzed. Samples were homogenized and sieved through 2 mm mesh. The mean proportion of organic carbon in Menjiko (t= 5.21, df=1, P<0.01) and in Gimbicho (t= –4.08, df=1, P<P0.05) revealed significant variation between wet and dry seasons. The mean proportion of total nitrogen was lower in GCHA (0.153 ±0.014) and higher in HADCHA (0.206±0.014) during the dry season. Hence, they showed significant variation (F1, 14= 7.06, P < 0.05) in the amount of total nitrogen. Mean sodium concentration in salt lick, common warthog ingested varied from 0.01 ±0.001Na meq/100g (Menjiko) to 0.08±0.006 meq/100g (Dodeta) during the dry season. However, the study areas were insignificantly different (F1,14=1.63, P > 0.05). Mean potassium concentration in salt lick common warthog ranged from 0.11±0.014 meq/100g (Desa) to 0.246±0.01meq/100g (Robe) during the wet season in Dabena Valley Forest (DVF). Warthogs supplemented their forage intake by licking different mineral elements from the ground. Mineral lick also benefits the animals in regulating the state body equilibrium and defending pathogens invading the animal’s body.


Introduction
Common warthogs salt lick mostly in the morning and afternoon hours [20]. The greatest peaks in visits of such sites occur from December to February [6,16,25]. The peak periods visit lick site coincide with plant phenology (variable timing of plant growth and forage preferences) [17,27]. The visitation periods associated with the increased physiological demands of growth, or weight regain, motivated by electrolyte loss related to stress of sudden changes in forage chemistry of the animal [6,16,26,29]. Common warthogs use wet ( Figure 1) and dry licks ( Figure 2) [6,17,26]. Wet lick is linked with the change in forage chemistry and the loss of sodium from sweat or urine is much more than other times of the year [26] and underground water springs [6]. Dry licks usually occur along streams or riverbeds because un weathered soluble elements are deposits above less firm layers, and become exposed by erosion as dry licks [6].
Salt licks contain high levels of essential minerals such as nitrogen, phosphorus, sodium, potassium, calcium and magnesium [12,16,20,21]. These essential minerals are lacking in the diets of animals [14,16]. Shortage of macro and micro elements are not necessarily result of inadequate dietary ingestion only, but rather of digestive disorders linked with spring forage alteration [6]. Hence, mammals of tropical savanna are obligated to supplement minerals from other sources to ensure enough nutrients in their diets [20,21,26].

Description of the Study Areas
Ethiopia is one of the East African countries rich in flora and fauna diversities.  [4,13]. Didessa and Dabus rivers drain the southwestern part of the basin, and contribute one third of the total flow of the Grand Ethiopian Renaissance Dam [11] which is the main sediment source of the Nile River [2]. Gassi controlled hunting area was demarcated as a controlled hunting area in 2007 with an estimated total area of 24,000 ha that includes Combretum-Terminalia woodland and riparian forest [1].

Haro Aba Diko Controlled Hunting Area (HADCHA)
Haro Aba Diko Controlled Hunting Area is located in the  Figure 4).
HADCHA was demarcated in 2007 with an estimated total area of 53,841 ha that includes savanna woodland and riparian forest. It is one of the controlled hunting areas in the western Ethiopia that could be used as the future carbon sequestration center of the country [1].

Methods
Salt licking data were collected from eight randomly allocated study sites. These include: Robe, Desa, Gimbicho, and Dodeta sites from HADCHA and Menjiko, Seba, Messio and Lemana sites from GCHA. Top soil samples licked by common warthog were taken from 2.5 cm diameter, 20 cm deep soil cores, from five evenly spaced locations around the periphery of the central 60x60 m grid in each feeding plot [15,23]. All samples from each feeding plot were pooled and thoroughly mixed for each study sites. A total of 32 kg soil samples were collected during the dry and wet seasons of 2017 and 2018 study periods. Soil collected from study plots were marked using GPS [8,10,34]. Soil samples were dried under shade for one week and then kept at 28°C until analyzed. Samples were homogenized and sieved through 2 mm mesh [3,15,30]. Soil samples were analyzed [33] at the Soil Laboratory of Holeta National Agricultural Research Center.

Data Analyses
Total N and C and nutrient content of P, Na, K, Ca, and Mg of soil samples ingested by warthogs were analyzed by inductively coupled plasma spectroscopy [3,15,20,32]. One-way ANOVA was used to test the differences between the chemical properties of the geophagical soils of the study sites [20]. Chi-square was used to analyze seasonal differences of ingested soil and data of descriptive statistics were presented as mean ± SE [20,25].
The mean phosphorous concentration in salt licking common warthog ranged from 4 Table 2).

Discussion
Salt or mineral lick influences the movements and distribution of ungulates [7,14] and physiologically against intestinal ailments associated with forage phenology and serve to supplement mineral intake [7,18]. It also maintains the equilibrium between the major minerals in the body of herbivorous mammals [18]. On the other hand, energetic costs to seek out mineral licks reduce time for foraging on vegetation [19]. Mineral elements are deficient in the diet of ungulates [7,29]. Similarly, common warthogs and other ungulates regularly consume soil in African savannas for seeking different mineral elements to meet their nutritional requirements [24,31]. Organic carbon buffers against disorders associated with wet season forage change, stabilizing pH in the stomach of ungulates and it is the main source of energy [5,19]. Likewise, in the present study, common warthogs ingested comparable mean proportion of organic carbon salt lick in GCHA and in HADCHA during the wet season. During the dry season, the mean proportion of organic carbon was lower in GCHA and higher in HADCHA. This might be due to natural licks are special habitat features and site-specific to maintain the health of ungulate populations [7]. The finding of the present study showed differences from [32], who described (OC=1.2±0.3) ingested by common warthogs in Mkwaja Ranch, Tanzania, was smaller than the finding of the present study.
During the present study, the mean total nitrogen proportion in salt licking common warthog ingested was higher in GCHA and less in HADCHA during the wet season. During the dry season, the mean proportion of total nitrogen was less in GCHA and higher in HADCHA. The finding of the present study was consistent with the finding of [32], who reported total nitrogen ingested by common warthog in Mkwaja Ranch in Tanzania. Phosphorous is one of the major mineral elements, which maintains an animal body [22]. In the present study, during the wet season the mean phosphorous concentration from salt lick common warthog ingested was less in GCHA and more in HADCHA. During the dry season, the mean concentration of phosphorous in GCHA and in HADCHA was comparable. This could be due to temporal and spatial patterns of licks visiting are different in the study areas and during season of year [26]. The finding of the present study was contradictory with [32], who found lower amount of phosphorous ingested by common warthog in Mkwaja Ranch in Tanzanian.
Na is a key driver of natural lick visitation [6]. During the dry season, grazing animals compensate for low Na concentration by visiting mineral springs, and saltimpregnated soils [9,28]. Thus, Na benefits ungulates in osmolarity regulation and compensate seasonal deficiencies in many forage plants [5]. In the present study, both study areas common warthogs ingested consistent meq/100g of Na in the salt lick during the wet and dry seasons. K ingested from earth licking elevates the osmotic pressure of the digestive tract and interferes with fecal water absorption. This leads to the loss of potentially harmful electrolyte and regulate acid-base equilibrium in animals [5,27]. Hence, in the present study, the mean K concentration in salt lick common warthog was smaller in GCHA and greater in HADCHA. In contrast, during the dry season, the mean concentration of K ingested from the salt lick was similar in both study areas.
Ca and Mg are motivating factors of natural lick visitation [6]. However, they are extensively used by ungulates [5]. Ca is the major mineral constituent of the animal body [21]. Mg levels make the forage sub-optimal for maintaining animal growth and body condition [5]. In the present study, similar mean of Mg and Ca concentration were in salt lick by common warthog in GCHA and HADCHA during the wet the dry seasons. This might be due to even distribution of these mineral elements in Dabena Valley Forests.

Conclusion
Common warthogs population supplemented their forage intake by licking different mineral elements from the ground to meet their nutritional requirements. Chemical composition of lick soil ingested by common warthog comprised mainly, organic carbon, nitrogen, phosphorous, sodium, potassium, magnesium and calcium. Hence, organic carbon and phosphorous ingested by common warthog was higher in present study area. Total nitrogen ingested by warthog in the present study area was consistent with other range of the animal. These mineral licks benefits warthogs to compensate seasonal deficiencies of many forage plants in Dabena Valley Forests.